Setting an expiry date or a maximum age in the HTTP headers for static resources instructs the browser to load previously downloaded resources from local disk rather than over the network.

Web/HTTP caching is the caching of web documents (e.g., HTML pages, images) to reduce bandwidth usage, server load, and perceived lag. A web cache stores copies of documents passing through it; subsequent requests may be satisfied from the cache if certain conditions are met.
Wikipedia

On the usual default settings, browsers will always check for freshness, using a conditional GET request. The server returns the date of last modification, and the browser compares this with the date from its cache. If the item has been changed, the browser will download it again.

Why Caching?

According to Google docs in its Optimize Caching tips:

Most web pages include resources that change infrequently, such as CSS files, image files, JavaScript files, and so on. These resources take time to download over the network, which increases the time it takes to load a web page.

HTTP caching allows these resources to be saved, or cached, by a browser or proxy. Once a resource is cached, a browser or proxy can refer to the locally cached copy instead of having to download it again on subsequent visits to the web page. Thus caching is a double win: you reduce round-trip time by eliminating numerous HTTP requests for the required resources, and you substantially reduce the total payload size of the responses. Besides leading to a dramatic reduction in page load time for subsequent user visits, enabling caching can also significantly reduce the bandwidth and hosting costs for your site.

Web page designs are getting richer and richer, which means more scripts, stylesheets, images, and Flash in the page. A first-time visitor to your page may have to make several HTTP requests, but by using the Expires header you make those components cacheable. This avoids unnecessary HTTP requests on subsequent page views. Expires headers are most often used with images, but they should be used on all components including scripts, stylesheets, and Flash components.
Yahoo: Best Practices for Speeding Up Your Web Site

What To Cache?

HTTP/S supports local caching of static resources by the browser. Some of the newest browsers (e.g. IE 7, Chrome) use a heuristic to decide how long to cache all resources that don’t have explicit caching headers. Other older browsers may require that caching headers be set before they will fetch a resource from the cache; and some may never cache any resources sent over SSL.

To take advantage of the full benefits of caching consistently across all browsers, we recommend that you configure your web server to explicitly set caching headers and apply them to all cacheable static resources, not just a small subset (such as images). Cacheable resources include JS and CSS files, image files, and other binary object files (media files, PDFs, Flash files, etc.).
Google: Leverage Browser Caching

In general, HTML is not static, and shouldn’t be considered cacheable.

How To Cache?

There are several tools that Web developers and Webmasters can use to fine-tune how caches will treat their sites. It may require getting your hands a little dirty with your server’s configuration, but the results are worth it. For this article, we are going to learn one of the method of controlling the browser cache with Apache HTTP server module (also known as htaccess Mod Rewrite)

The modules need to be built into Apache; although they are included in the distribution, they are not turned on by default. Some Apache server turn on the module by default tho. If they are not available to you, then you need to contact your server administrator. The modules we’re looking for are mod_expires.

HTTP Caching With Htaccess (with mod_expires module)

Here’s an example .htaccess file that demonstrates how to set far-future expiry for your static assets.

###################################
#   HTTP Header Caching Setting   #
###################################
# Set far-future expiry for images, css, and js
# Remember that you MUST change the filename whenever you update these items!
# Enablel this in your httpd.conf :
# LoadModule expires_module modules/mod_expires.so
<ifmodule mod_expires.c>
<Filesmatch "\.(jpg|jpeg|png|gif|js|css|swf|ico)$">
    ExpiresActive on
    ExpiresDefault "access plus 1 years"
</Filesmatch>
</ifmodule>

This aggressively caches all static assets (images, and so on), but not the pages themselves. A consequence is that, whenever you change a file (say, you alter your CSS), you must also change its name (add a version number or date-stamp).

For all cacheable resources (images, css, js), it is recommend to set the expires date not greater than one year in the future. Setting it more than one year will violates the RFC guidelines.

If you know exactly when a resource is going to change, setting a shorter expiration is okay. But if you think it “might change soon” but don’t know when, you should set a long expiration. Setting caching aggressively does not “pollute” browser caches: as far as we know, all browsers clear their caches according to a Least Recently Used algorithm; we are not aware of any browsers that wait until resources expire before purging them.

This kind of caching is far too aggressive for a web page, as the contents of the page may change, and you really don’t want to change the URL! However, caching the page is not very important, compared to caching the associated files.

Those commands set a 1-year expiry date for all my CSS, javascript, and image files. This means that the browser won’t even check for new versions until 1 years later.

Forcing The Browser To Apply A New Changes

What happens if you change your logo after one month? What happen if you made some changes to your CSS file? There’s no way for the user to get the new logo or the new style, unless he refreshes the web page. And why would they do that?

The solution is to change the file name. If the file was called logo1.png, you rename it to logo2.png (and you also change any references to it in your code). Then the browser will download it again, because as far as the browser is concerned, it’s a completely different file. Each time you change the logo, increment the version suffix by 1 (alternatively, you can use a date-stamp. Just make sure it’s always a file name you haven’t used before).

Example:

<link rel="stylesheet" type="text/css" href="style.css?date=13-12-2010">
<link rel="stylesheet" type="text/css" href="style.css?v=1.0">

Let’s Test Our Page!

Now that we have the htaccess ready in our web server, it is time to test them and see the comparison visually.

Scenario #1 (2 HTTP Request)

Normally, the conversation between browser and server goes like this:

1. Browser: send me that web page please [HTTP request number 1]
2. Server: sure, here it is. You will also need this large logo image
3. Browser: let me just check if I’ve got it already…yes, but that was yesterday. I guess it might have been updated since then. Can you tell me when it was last modified? [HTTP request number 2]
4. Server: sure. It was last modified a year ago
5. Browser: okay, my cached version is more recent than that. I don’t need to download it again

So you can see that there are two HTTP requests, two separate occasions when the browser asks the server for data. First it asks for the web page, then it asks when the logo was last modified.

This is how caching normally works. Yslow is recommending more aggressive caching, where you send expiry information along with the file. With the .htaccess commands I gave you, the conversation between server and browser will be different:

Scenario #2 (1 HTTP Request)

• Browser: send me that web page please [HTTP request number 1]
• Server: sure, here it is. You will also need this large logo image
• Browser: let me just check if I’ve got it already…yes, and it doesn’t expire for another 1 years. I can use my cached version

So this time, there’s only one HTTP request. Yet there’s a catch! The browser will never ask for a fresh version. It won’t even ask whether the image has been modified. The same thing goes with your CSS, js and the rest of your static assets file.

A Visual Comparison

First, let’s start of by loading a fresh new website into our browser. The following image (captured with HTTPWatch) showing the time line of the page loading time by displaying the detail page resources versus the time it takes to load that individual resources.

The requests from browsers, result in one of the following response status codes:

• 200 – The browser does not have the image in its cache. [First time visit]
• 304 – The browser has the image in its cache, but needs to verify the last modified date.

We can see that the time it takes for the web browser to loads this page is approximately 3.5 seconds from as seen from the Time column.

Now, let’s have a look on how our browser loads our page with a locally cached copy of all the static elements!

As you can see, the page loads almost 50% faster that the previous one which is approximately 1.6 seconds. All the blue line that you see from the time chart representing the locally cached copy of all the web page resources.

Summary

Using a far future Expires header affects page views only after a user has already visited your site. It has no effect on the number of HTTP requests when a user visits your site for the first time and the browser’s cache is empty. Therefore the impact of this performance improvement depends on how often users hit your pages with a primed cache. (A “primed cache” already contains all of the components in the page.)

By using a far future Expires header, you increase the number of components that are cached by the browser and re-used on subsequent page views without sending a single byte over the user’s Internet connection. In simple terms, it:

• Reduce round-trip
• Avoids unnecessary HTTP requests
• Reduce bandwidth usage
• Reduce server load
• …and you get a faster loading page!

1.1 Informational 1xx

This class of status code indicates a provisional response, consisting only of the Status-Line and optional headers, and is terminated by an empty line. There are no required headers for this class of status code. Since HTTP/1.0 did not define any 1xx status codes, servers MUST NOT send a 1xx response to an HTTP/1.0 client except under experimental conditions.

A client MUST be prepared to accept one or more 1xx status responses prior to a regular response, even if the client does not expect a 100 (Continue) status message. Unexpected 1xx status responses MAY be ignored by a user agent.

Proxies MUST forward 1xx responses, unless the connection between the proxy and its client has been closed, or unless the proxy itself requested the generation of the 1xx response. (For example, if a proxy adds a “Expect: 100-continue” field when it forwards a request, then it need not forward the corresponding 100 (Continue) response(s).)

1.1.1 100 Continue

The client SHOULD continue with its request. This interim response is used to inform the client that the initial part of the request has been received and has not yet been rejected by the server. The client SHOULD continue by sending the remainder of the request or, if the request has already been completed, ignore this response. The server MUST send a final response after the request has been completed. See section 8.2.3 for detailed discussion of the use and handling of this status code.

1.1.2 101 Switching Protocols

The server understands and is willing to comply with the client’s request, via the Upgrade message header field, for a change in the application protocol being used on this connection. The server will switch protocols to those defined by the response’s Upgrade header field immediately after the empty line which terminates the 101 response.

The protocol SHOULD be switched only when it is advantageous to do so. For example, switching to a newer version of HTTP is advantageous over older versions, and switching to a real-time, synchronous protocol might be advantageous when delivering resources that use such features.

1.2 Successful 2xx

This class of status code indicates that the client’s request was successfully received, understood, and accepted.

1.2.1 200 OK

The request has succeeded. The information returned with the response is dependent on the method used in the request, for example:

• GET an entity corresponding to the requested resource is sent in the response;
• HEAD the entity-header fields corresponding to the requested resource are sent in the response without any message-body;
• POST an entity describing or containing the result of the action;
• TRACE an entity containing the request message as received by the end server.

1.2.2 201 Created

The request has been fulfilled and resulted in a new resource being created. The newly created resource can be referenced by the URI(s) returned in the entity of the response, with the most specific URI for the resource given by a Location header field. The response SHOULD include an entity containing a list of resource characteristics and location(s) from which the user or user agent can choose the one most appropriate. The entity format is specified by the media type given in the Content-Type header field. The origin server MUST create the resource before returning the 201 status code. If the action cannot be carried out immediately, the server SHOULD respond with 202 (Accepted) response instead.

A 201 response MAY contain an ETag response header field indicating the current value of the entity tag for the requested variant just created.

1.2.3 202 Accepted

The request has been accepted for processing, but the processing has not been completed. The request might or might not eventually be acted upon, as it might be disallowed when processing actually takes place. There is no facility for re-sending a status code from an asynchronous operation such as this.

The 202 response is intentionally non-committal. Its purpose is to allow a server to accept a request for some other process (perhaps a batch-oriented process that is only run once per day) without requiring that the user agent’s connection to the server persist until the process is completed. The entity returned with this response SHOULD include an indication of the request’s current status and either a pointer to a status monitor or some estimate of when the user can expect the request to be fulfilled.

1.2.4 203 Non-Authoritative Information

The returned metainformation in the entity-header is not the definitive set as available from the origin server, but is gathered from a local or a third-party copy. The set presented MAY be a subset or superset of the original version. For example, including local annotation information about the resource might result in a superset of the meta information known by the origin server. Use of this response code is not required and is only appropriate when the response would otherwise be 200 (OK).

1.2.5 204 No Content

The server has fulfilled the request but does not need to return an entity-body, and might want to return updated meta information. The response MAY include new or updated meta information in the form of entity-headers, which if present SHOULD be associated with the requested variant.

If the client is a user agent, it SHOULD NOT change its document view from that which caused the request to be sent. This response is primarily intended to allow input for actions to take place without causing a change to the user agent’s active document view, although any new or updated meta information SHOULD be applied to the document currently in the user agent’s active view.

The 204 response MUST NOT include a message-body, and thus is always terminated by the first empty line after the header fields.

1.2.6 205 Reset Content

The server has fulfilled the request and the user agent SHOULD reset the document view which caused the request to be sent. This response is primarily intended to allow input for actions to take place via user input, followed by a clearing of the form in which the input is given so that the user can easily initiate another input action. The response MUST NOT include an entity.

1.2.7 206 Partial Content

The server has fulfilled the partial GET request for the resource. The request MUST have included a Range header field indicating the desired range, and MAY have included an If-Range header field (section 14.27) to make the request conditional.

The response MUST include the following header fields:

• Either a Content-Range header field (section 14.16) indicating the range included with this response, or a multipart/byteranges Content-Type including Content-Range fields for each part. If a Content-Length header field is present in the response, its value MUST match the actual number of OCTETs transmitted in the message-body.
• Date
• ETag and/or Content-Location, if the header would have been sent in a 200 response to the same request
• Expires, Cache-Control, and/or Vary, if the field-value might differ from that sent in any previous response for the same variant

If the 206 response is the result of an If-Range request that used a strong cache validator, the response SHOULD NOT include other entity-headers. If the response is the result of an If-Range request that used a weak validator, the response MUST NOT include other entity-headers; this prevents inconsistencies between cached entity-bodies and updated headers. Otherwise, the response MUST include all of the entity-headers that would have been returned with a 200 (OK) response to the same request.

A cache MUST NOT combine a 206 response with other previously cached content if the ETag or Last-Modified headers do not match exactly,see 13.5.4.

A cache that does not support the Range and Content-Range headers MUST NOT cache 206 (Partial) responses.

1.3 Redirection 3xx

This class of status code indicates that further action needs to be taken by the user agent in order to fulfill the request. The action required MAY be carried out by the user agent without interaction with the user if and only if the method used in the second request is GET or HEAD. A client SHOULD detect infinite redirection loops, since such loops generate network traffic for each redirection.

Note: previous versions of this specification recommended a maximum of five redirections. Content developers should be aware that there might be clients that implement such a fixed limitation.

1.3.1 300 Multiple Choices

The requested resource corresponds to any one of a set of representations, each with its own specific location, and agent- driven negotiation information is being provided so that the user (or user agent) can select a preferred representation and redirect its request to that location.

Unless it was a HEAD request, the response SHOULD include an entity containing a list of resource characteristics and location(s) from which the user or user agent can choose the one most appropriate. The entity format is specified by the media type given in the Content- Type header field. Depending upon the format and the capabilities of

the user agent, selection of the most appropriate choice MAY be performed automatically. However, this specification does not define any standard for such automatic selection.

If the server has a preferred choice of representation, it SHOULD include the specific URI for that representation in the Location field; user agents MAY use the Location field value for automatic redirection. This response is cacheable unless indicated otherwise.

1.3.2 301 Moved Permanently

The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD use one of the returned URIs. Clients with link editing capabilities ought to automatically re-link references to the Request-URI to one or more of the new references returned by the server, where possible. This response is cacheable unless indicated otherwise.

The new permanent URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s).

If the 301 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued.

Note: When automatically redirecting a POST request after receiving a 301 status code, some existing HTTP/1.0 user agents will erroneously change it into a GET request.

1.3.3 302 Found

The requested resource resides temporarily under a different URI. Since the redirection might be altered on occasion, the client SHOULD continue to use the Request-URI for future requests. This response is only cache-able if indicated by a Cache-Control or Expires header field.

The temporary URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s).

If the 302 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued.

Note: RFC 1945 and RFC 2068 specify that the client is not allowed to change the method on the redirected request. However, most existing user agent implementations treat 302 as if it were a 303 response, performing a GET on the Location field-value regardless of the original request method. The status codes 303 and 307 have been added for servers that wish to make unambiguously clear which kind of reaction is expected of the client.

1.3.4 303 See Other

The response to the request can be found under a different URI and SHOULD be retrieved using a GET method on that resource. This method exists primarily to allow the output of a POST-activated script to redirect the user agent to a selected resource. The new URI is not a substitute reference for the originally requested resource. The 303 response MUST NOT be cached, but the response to the second (redirected) request might be cache-able.

The different URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s).

Note: Many pre-HTTP/1.1 user agents do not understand the 303 status. When interoperability with such clients is a concern, the 302 status code may be used instead, since most user agents react to a 302 response as described here for 303.

1.3.5 304 Not Modified

If the client has performed a conditional GET request and access is allowed, but the document has not been modified, the server SHOULD respond with this status code. The 304 response MUST NOT contain a message-body, and thus is always terminated by the first empty line after the header fields.

The response MUST include the following header fields:

• Date, unless its omission is required by section 14.18.1
  If a clockless origin server obeys these rules, and proxies and clients add their own Date to any response received without one (as already specified by [RFC 2068], section 14.19), caches will operate correctly.
• ETag and/or Content-Location, if the header would have been sent in a 200 response to the same request
• Expires, Cache-Control, and/or Vary, if the field-value might differ from that sent in any previous response for the same variant

If the conditional GET used a strong cache validator (see section 13.3.3), the response SHOULD NOT include other entity-headers. Otherwise (i.e., the conditional GET used a weak validator), the response MUST NOT include other entity-headers; this prevents inconsistencies between cached entity-bodies and updated headers.

If a 304 response indicates an entity not currently cached, then the cache MUST disregard the response and repeat the request without the conditional.

If a cache uses a received 304 response to update a cache entry, the cache MUST update the entry to reflect any new field values given in the response.

1.3.6 305 Use Proxy

The requested resource MUST be accessed through the proxy given by the Location field. The Location field gives the URI of the proxy. The recipient is expected to repeat this single request via the proxy. 305 responses MUST only be generated by origin servers.

Note: RFC 2068 was not clear that 305 was intended to redirect a single request, and to be generated by origin servers only. Not observing these limitations has significant security consequences.

1.3.7 306 (Unused)

The 306 status code was used in a previous version of the specification, is no longer used, and the code is reserved.

1.3.8 307 Temporary Redirect

The requested resource resides temporarily under a different URI. Since the redirection MAY be altered on occasion, the client SHOULD continue to use the Request-URI for future requests. This response is only cacheable if indicated by a Cache-Control or Expires header field.

The temporary URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s) , since many pre-HTTP/1.1 user agents do not understand the 307 status. Therefore, the note SHOULD contain the information necessary for a user to repeat the original request on the new URI.

If the 307 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued.

1.4 Client Error 4xx

The 4xx class of status code is intended for cases in which the client seems to have erred. Except when responding to a HEAD request, the server SHOULD include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition. These status codes are applicable to any request method. User agents SHOULD display any included entity to the user.

If the client is sending data, a server implementation using TCP SHOULD be careful to ensure that the client acknowledges receipt of the packet(s) containing the response, before the server closes the input connection. If the client continues sending data to the server after the close, the server’s TCP stack will send a reset packet to the client, which may erase the client’s unacknowledged input buffers before they can be read and interpreted by the HTTP application.

1.4.1 400 Bad Request

The request could not be understood by the server due to malformed syntax. The client SHOULD NOT repeat the request without modifications.

1.4.2 401 Unauthorized

The request requires user authentication. The response MUST include a WWW-Authenticate header field (section 14.47) containing a challenge applicable to the requested resource. The client MAY repeat the request with a suitable Authorization header field (section 14.8). If the request already included Authorization credentials, then the 401 response indicates that authorization has been refused for those credentials. If the 401 response contains the same challenge as the prior response, and the user agent has already attempted authentication at least once, then the user SHOULD be presented the entity that was given in the response, since that entity might include relevant diagnostic information. HTTP access authentication is explained in “HTTP Authentication: Basic and Digest Access Authentication” [43].

1.4.3 402 Payment Required

This code is reserved for future use.

1.4.4 403 Forbidden

The server understood the request, but is refusing to fulfill it. Authorization will not help and the request SHOULD NOT be repeated. If the request method was not HEAD and the server wishes to make public why the request has not been fulfilled, it SHOULD describe the reason for the refusal in the entity. If the server does not wish to make this information available to the client, the status code 404 (Not Found) can be used instead.

1.4.5 404 Not Found

The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent. The 410 (Gone) status code SHOULD be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable and has no forwarding address. This status code is commonly used when the server does not wish to reveal exactly why the request has been refused, or when no other response is applicable.

1.4.6 405 Method Not Allowed

The method specified in the Request-Line is not allowed for the resource identified by the Request-URI. The response MUST include an Allow header containing a list of valid methods for the requested resource.

1.4.7 406 Not Acceptable

The resource identified by the request is only capable of generating response entities which have content characteristics not acceptable according to the accept headers sent in the request.

Unless it was a HEAD request, the response SHOULD include an entity containing a list of available entity characteristics and location(s) from which the user or user agent can choose the one most appropriate. The entity format is specified by the media type given in the Content-Type header field. Depending upon the format and the capabilities of the user agent, selection of the most appropriate choice MAY be performed automatically. However, this specification does not define any standard for such automatic selection.

Note: HTTP/1.1 servers are allowed to return responses which are not acceptable according to the accept headers sent in the request. In some cases, this may even be preferable to sending a 406 response. User agents are encouraged to inspect the headers of an incoming response to determine if it is acceptable.

If the response could be unacceptable, a user agent SHOULD temporarily stop receipt of more data and query the user for a decision on further actions.

1.4.8 407 Proxy Authentication Required

This code is similar to 401 (Unauthorized), but indicates that the client must first authenticate itself with the proxy. The proxy MUST return a Proxy-Authenticate header field (section 14.33) containing a challenge applicable to the proxy for the requested resource. The client MAY repeat the request with a suitable Proxy-Authorization header field (section 14.34). HTTP access authentication is explained in “HTTP Authentication: Basic and Digest Access Authentication”[43].

1.4.9 408 Request Timeout

The client did not produce a request within the time that the server was prepared to wait. The client MAY repeat the request without modifications at any later time.

1.4.10 409 Conflict

The request could not be completed due to a conflict with the current state of the resource. This code is only allowed in situations where it is expected that the user might be able to resolve the conflict and resubmit the request. The response body SHOULD include enough information for the user to recognize the source of the conflict. Ideally, the response entity would include enough information for the user or user agent to fix the problem; however, that might not be possible and is not required.

Conflicts are most likely to occur in response to a PUT request. For example, if versioning were being used and the entity being PUT included changes to a resource which conflict with those made by an earlier (third-party) request, the server might use the 409 response to indicate that it can’t complete the request. In this case, the response entity would likely contain a list of the differences between the two versions in a format defined by the response Content-Type.

1.4.11 410 Gone

The requested resource is no longer available at the server and no forwarding address is known. This condition is expected to be considered permanent. Clients with link editing capabilities SHOULD delete references to the Request-URI after user approval. If the server does not know, or has no facility to determine, whether or not the condition is permanent, the status code 404 (Not Found) SHOULD be used instead. This response is cacheable unless indicated otherwise.

The 410 response is primarily intended to assist the task of web maintenance by notifying the recipient that the resource is intentionally unavailable and that the server owners desire that remote links to that resource be removed. Such an event is common for limited-time, promotional services and for resources belonging to individuals no longer working at the server’s site. It is not necessary to mark all permanently unavailable resources as “gone” or to keep the mark for any length of time — that is left to the discretion of the server owner.

1.4.12 411 Length Required

The server refuses to accept the request without a defined Content- Length. The client MAY repeat the request if it adds a valid Content-Length header field containing the length of the message-body in the request message.

1.4.13 412 Precondition Failed

The precondition given in one or more of the request-header fields evaluated to false when it was tested on the server. This response code allows the client to place preconditions on the current resource metainformation (header field data) and thus prevent the requested method from being applied to a resource other than the one intended.

1.4.14 413 Request Entity Too Large

The server is refusing to process a request because the request entity is larger than the server is willing or able to process. The server MAY close the connection to prevent the client from continuing the request.

If the condition is temporary, the server SHOULD include a Retry- After header field to indicate that it is temporary and after what time the client MAY try again.

1.4.15 414 Request-URI Too Long

The server is refusing to service the request because the Request-URI is longer than the server is willing to interpret. This rare condition is only likely to occur when a client has improperly converted a POST request to a GET request with long query information, when the client has descended into a URI “black hole” of redirection (e.g., a redirected URI prefix that points to a suffix of itself), or when the server is under attack by a client attempting to exploit security holes present in some servers using fixed-length buffers for reading or manipulating the Request-URI.

1.4.16 415 Unsupported Media Type

The server is refusing to service the request because the entity of the request is in a format not supported by the requested resource for the requested method.

1.4.17 416 Requested Range Not Satisfiable

A server SHOULD return a response with this status code if a request included a Range request-header field (section 14.35), and none of the range-specifier values in this field overlap the current extent of the selected resource, and the request did not include an If-Range request-header field. (For byte-ranges, this means that the first- byte-pos of all of the byte-range-spec values were greater than the current length of the selected resource.)

When this status code is returned for a byte-range request, the response SHOULD include a Content-Range entity-header field specifying the current length of the selected resource (see section 14.16). This response MUST NOT use the multipart/byteranges content- type.

1.4.18 417 Expectation Failed

The expectation given in an Expect request-header field (see section 14.20) could not be met by this server, or, if the server is a proxy, the server has unambiguous evidence that the request could not be met by the next-hop server.

1.5 Server Error 5xx

Response status codes beginning with the digit “5″ indicate cases in which the server is aware that it has erred or is incapable of performing the request. Except when responding to a HEAD request, the server SHOULD include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition. User agents SHOULD display any included entity to the user. These response codes are applicable to any request method.

1.5.1 500 Internal Server Error

The server encountered an unexpected condition which prevented it from fulfilling the request.

1.5.2 501 Not Implemented

The server does not support the functionality required to fulfill the request. This is the appropriate response when the server does not recognize the request method and is not capable of supporting it for any resource.

1.5.3 502 Bad Gateway

The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting to fulfill the request.

1.5.4 503 Service Unavailable

The server is currently unable to handle the request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay. If known, the length of the delay MAY be indicated in a Retry-After header. If no Retry-After is given, the client SHOULD handle the response as it would for a 500 response.

Note: The existence of the 503 status code does not imply that a server must use it when becoming overloaded. Some servers may wish to simply refuse the connection.

1.5.5 504 Gateway Timeout

The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server specified by the URI (e.g. HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed to access in attempting to complete the request.

Note: Note to implementors: some deployed proxies are known to return 400 or 500 when DNS lookups time out.

1.5.6 505 HTTP Version Not Supported

The server does not support, or refuses to support, the HTTP protocol version that was used in the request message. The server is indicating that it is unable or unwilling to complete the request using the same major version as the client, as described in section 3.1, other than with this error message. The response SHOULD contain an entity describing why that version is not supported and what other protocols are supported by that server.

The following guide is on how to activate older non OEM activation codes to upgrade to 2011.

A Quick Facts

• Retail 2009/2010 activation codes cannot be activated within Retail 2011 software
• Retail 2009/2010 activation codes (OEM) cannot be upgraded. We have only given out OEM codes for free. So all sold codes are non-OEM.
• Retail 2009/2010 activation codes must be activated before using the new Retail 2011 software

Here are the steps to activate and start using Retail 2011 software with 2009/2010 activation code!

Step 1: Web Activation

Register the activation code in Panda Security Website at http://www.pandasecurity.com/homeusers/support/register/

Step 2: Copy Client Number

Upon completion, you will get the expiry date and client no. An email will also be sent.

Step 3: Download The Latest Version

Download, install and activate the Retail 2011 application using the retail 2009/2010 activation code and client no.

• Panda Antivirus Pro 2011: http://files.pandasecurity.com.my/files/APAC/Retail 2011/Localization/ESD/AP11.exe (68 MB)
• Panda Internet Security 2011: http://files.pandasecurity.com.my/files/APAC/Retail 2011/Localization/ESD/IS11.exe (73 MB)
• Panda Global Protection 2011: http://files.pandasecurity.com.my/files/APAC/Retail 2011/Localization/ESD/GP11.exe (73 MB)
• Panda Internet security for Netbooks 2011: http://files.pandasecurity.com.my/files/APAC/Retail 2011/Localization/ESD/PNT11.exe (72 MB)

For further detail information, visit Panda Antivirus official website!

Up Coming Event!

Soon, Monie Studios will be conducting yet another fun event and of course there will be a lot of prizes to be won! Here is the event that will took place soon:

• Panda Antivirus Freebies Giveaway
• Web Design Article Competition

Here are several ways to keep yourself updated with Moniestudios.com. Stay tuned!

1. Facebook
2. Twitter

Before We Start?

Before changing your website old domain name into your brand newly purchased domain name, there is a few issue that you need to keep in mind, and the most important one are the 404 error.

You don’t want your visitors to get frustrated with getting a lot of 404 error message. It will somehow give a negative impression to your website and again, you really don’t want to do that!

Let’s Get Started With Our .htaccess File

If your web server is using Apache HTTP Server then you can use the powerful mod_rewrite module to do the task. It required only few lines of code.

Create a “.htaccess” file in your oldDomain’s web root folder(example: /public_html/) then enter the following codes in the file.

RewriteEngine on
RewriteCond %{HTTP_HOST} ^oldDomain.com$ [OR]
RewriteCond %{HTTP_HOST} ^www.oldDomain.com$
RewriteRule ^(.*)$ http://www.newDomain.com/$1 [R=301,L]

Done! Now all your visitors will be redirected from oldDomain.com(regardless the path) to newDomain.com

Happy redirecting…

Illustrator itself has always been a print based application and one thing it just doesn’t do is animation.

There is an application called Adobe Flash. Flash does have the ability to create animation. It’s also one of the most popular applications being used to create animation. Flash uses the concept of framed based animation whereas in Illustrator, there is no frame. However, there are layers inside Illustrator and the beauty of Illustrator is that it can turn layers into frames for you.

Let’s see how we can do that.

Creating Layers

Opening my layers panel will show you that my banner is made up of 5 different layers. If you are familiar with the Flash application, you’ll know how easy it is to create an image like that. Now, just think of a layer as a frame and you’ll see how easy this will be.

What I have done here is basically to put every frame of my animation onto a separate layer. Right now I have five different layers and when combined, it will produce the full image like the example above.

Once you have completed setting up your layers, let’s create our animation.

Saving Your Animation

Things to consider when setting up the Save for Web & Devices command:

• Optimized file format: SWF
• Flash Player version: Flash Player 9 (the latest version on your machine)
• Type of export: Layers to SWF Frames (this is the most important setting)
• Curve Quality: 7
• Frame Rate: 1 second
• Loop: Play animation repeatedly (tick this checkbox)

Saving the file to SWF, a Flash format, Illustrator will ask you which flash player you want to optimize. Select Flash Player 9 which is the latest version at the time of writing this tutorial.

Type of export, this is the most important setting that you need to set. You can tell Illustrator to save your file into a big flash file by selecting the AI File to SWF File. You can also turn all your Illustrator layers into frames by selecting the second option which is Layers to SWF Frames and that’s going to create an animation.

Next, if you want to play the animation over and over again, put a tick in the Loop check box. Setting the frame rate to one frame per second means that every one second it’s going to switch within the layer.

Let’s go ahead and save the animation and select HTML and Images (*.html) in the Save as type. This will then automatically export an html demo file with the table already in it, so on and so forth.

This is how your html will look like, automatically generated for you by Illustrator.

<html>
<head>
<title>Simple-Animation-In-Illustrator-2</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><script src="images/Simple-Animation-with-Illustrator.js" type="text/javascript" ></script>
</head>
<body bgcolor="#FFFFFF" leftmargin="0" topmargin="0" marginwidth="0" marginheight="0"><noscript>
<!-- ImageReady Slices (Simple-Animation-with-Illustrator.ai) -->
<embed src="images/Simple-Animation-with-Illustrator.swf" width="569" height="80" alt="" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/shockwave/download/">
<!-- End ImageReady Slices --></noscript><script type="text/javascript">fn00000()</script>
</body>
</html>

See It In Action

Click here to view demo!

Note The default Remote Desktop Connection Client for Windows XP Professional is 3389.

You can use the Remote Desktop feature in Microsoft Windows XP Professional to connect to your computer from another remote computer. To change the port that Remote Desktop listens on, follow these simple steps.

Changing The Default Windows XP Pro RDP Port Number

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs.

1. Start Registry Editor. (regedit)
2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control \TerminalServer\WinStations\RDP-Tcp\PortNumber
3. On the Edit menu, click Modify, and then click Decimal.
4. Type the new port number, and then click OK.
5. Quit Registry Editor.

You have successfully changed your default RDP port number at this point.

Note When you try to connect to this computer by using the Remote Desktop connection, you must type the new port.

Port Forwarding Your Firewall To RDP To Your Computer

Once you have successfully changed your Windows XP default port number, it is time to do another trick (configuration in your firewall) to port forward your newly created RDP port number to point to your computer. Here is the setting and it may vary from different types/model of firewall.

Alternative To Windows RDP

You can use some third party application to access into your computer in a similar way by using any of this following application:

• Real VNC
• TeamViewer
• Ultra VNC
• LogMeIn

Hope this helps you with your RDP activity.

Download High resolution Here!

I have information spread out across a few databases and want to put all the information onto one webpage using PHP. I was wondering how I can connect to multiple databases on a single PHP webpage.

The Solution

You can make multiple calls to mysql_connect(), but if the parameters are the same you need to pass the value “true” as the forth parameter, otherwise the same connection is reused. Here is a demonstration on connecting multiple MySQL databases on a single Page.

Database One

    // Database ONE Connection

    // Constant variable declaration
    $host = 'localhost';
    $user = 'database_user';
    $pass = 'password';
    $name = 'database_name';

    // 1. Create database connection
    $db1_connection = mysql_connect($host, $user, $pass) or die(mysql_error());

    // 2. Select database to use
    $db1 = mysql_select_db($qn_name, $db1_connection) or die(mysql_error());

Database Two

    // Database TWO Connection

    // 1. Create the second database connection
    // Passing the "true" value in the forth parameter here
    $db2_connection = mysql_connect($host, $user, $pass, true) or die(mysql_error());

    // 2. Select database to use
    $db2 = mysql_select_db($name, $db2_connection) or die(mysql_error());

Problem solved! Happy coding…

<a href="http://bit.ly/asSkuN">MonieStudios.com</a>

Introduction To URL Shortening Services

One of the most popular URL shortening services is Bit.ly, which you see a lot in your twitter post link sharing. Bit.ly requires you to sign up for an account and once you have an account, you may attain your login detail, your appkey (you can find your appkey by clicking your username link) and your URL information. That is where you will be doing your URL shortening activity manually.

Most CMS like WordPress have a plugins of built in support for this service where you don’t have to be logged in to Bit.ly in order for you to shorten your link. It will be done right at your page just before it passed on to your twitter account.

What if you want to do the same thing with your custom made website. After all, custom made website doesn’t have shortening URL plugins like WordPress do!

I’ll show you how to create Bit.ly URLs remotely with PHP function.

The Functions

/* make a URL small with bit.ly */
function make_bitly_url($url,$login,$appkey,$format = 'xml',$version = '2.0.1') {

    //create the URL
    $bitly = 'http://api.bit.ly/shorten?version='.$version.'&longUrl='.urlencode($url).'&login='.$login.'&apiKey='.$appkey.'&format='.$format;

    //get the url, could also use cURL here
    $response = file_get_contents($bitly);

    //parse depending on desired format
    if(strtolower($format) == 'json') {
        $json = @json_decode($response,true);
        return $json['results'][$url]['shortUrl'];
    }
     //xml
    else {
        $xml = simplexml_load_string($response);
        return 'http://bit.ly/'.$xml->results->nodeKeyVal->hash;
    }
}

The Usage

Just put this code where you want to share the page to your social boorkmark (facebook, twitter, etc..). Your new URL that has been shorten can be access with the variable: $short

Example of usage would be something like this:

    // Get the full address of your website page
    $url = "http://".$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];

    // Authentication details
    $login = "your.email.id@gmail.com";
    $appkey = "R_22c9bc44570b459ab9d095d7ef5e78fe";

    /* Calling up the function */
    $short = make_bitly_url($url,$login,$appkey,'json');

    /* Share on Twitter link */
    <a class="twitter" href="http://twitter.com/home?status=Your Website Title - <?php echo $short; ?>">Twitter</a>

Happy shortening!