A textual description of the current rule, automatically assembled from the basic rule behavior settings contained in this tab. For example, changes to the URL test string or rule mode will be automatically reflected in the descriptive text in this field. It is possible to override this text with your own description, however no further automatic updates will be made.

To reset the description back to the default auto-generated string, click the reset button.

Web Content Accelerator can be set to accelerate or exclude all pages and resources identified by this rule.

Accelerate mode is the default, and performs the desired optimization defined within the rule properties on a matching request.

The alternative is to set the rule to exclude optimization for pages or resources that match the supplied URL test.

A third mode, strip, strips out resource references where a match is encountered.

These rules only apply to requests that match the specified text. The text is compared with the full URL including the hostname if the Match external resources box is checked, otherwise it is compared only with the URL path. You can specify a substring that must be contained in the URL, or a wildcard or regular expression that must match the entire URL.

Before using regular expressions, read and understand the security considerations in Using Regular Expressions.

This setting allows you match against resources held external to the Web application. If enabled, the rule will only match requests for hosts that are not included in the Application Scope, and the string contained in the URL test field will be matched against the hostname and path contained in the request. For example, you may wish to exclude media files on your Web page that are included from an external media hosting Web site. If this is the case, you can select this option and specify a wild-carded string in the URL test field that includes the name of the hosting site in addition to the URL path of the media files you are interested in.

None: Style sheets will remain in their original form wherever they appear.

Optimize CSS Content: Style sheet blocks in the page and in external style sheets will have all redundant whitespace and comments removed.

…and combine consecutive stylesheets: Style sheets that appear as consecutive references (i.e. without inline style blocks or excluded style sheet links between) will be combined and each combined reference inserted to the location where the first style sheet in a set appears in the document.

…and combine all stylesheets: All style sheets will be combined, no matter where they appear in the page. The new combined reference will be inserted at the top of the head section of the document.

Enabled: Images that appear as <img> tags in the HTML are combined using one of the following techniques:

CSS image spriting: Images are combined into an image sprite according to the image format.

Image streaming: Images are combined into one or more image streams.

Disabled: Images that appear as <img> tags in the HTML are not combined.

Images are shrunk where possible, removing unnecessary information such as metadata, redundant color information and in the case of JPEG images, reducing the quality to reduce the size of the files.

If an image appears on a Web page in BMP format, the Traffic Manager automatically converts it to JPEG format to reduce its size. You can prevent this by using a rule to exclude the image from being processed.

The percentage quality level to resample lossy images to (0-100). If retaining the quality of your images is paramount, set this value to 100.

The default is 85.

Allow images to be optimized to a different format than the original. The format can be chosen explicitly, or set to "Optimal", which chooses the best format automatically for each image.

Auto: Web Content Accelerator determines whether to cache a resource based on its content type. Static resources, such as style sheets and images are always cached, whereas dynamic resources, such as JSON-formatted API responses, obey the response's “Cache-Control” directives.

Always: Web Content Accelerator obeys all “Cache-Control” directives in the response.

Never: Web Content Accelerator caches all content it optimizes.

Enabled: URLs at this location are versioned by rewriting the URL to contain a hash of the contents of the file. The cache expiry time for versioned URLs is 1 year.

Disabled: URLs are unaltered and clients cache the item for the full Cache on browser interval before rechecking.

For more information, see Resource Naming and URL Versioning.

Enabled: Resources that are cacheable at this location will be marked with the “Cache-Control” public header that allows them to be cached by intermediary proxy servers.

Disabled: Resources that are cacheable will be marked with the “Cache-Control” private header to prevent them from being cached by intermediary proxy servers.

Enabled: If a resource such as an image or CSS stylesheet is requested by its original URL, enabling this option will cause Web Content Accelerator to optimize and cache the resource before returning it to the client. This can be useful if, for example, your site contains JavaScript that fetches images or other resources from your server after the page has loaded.

Disabled: Directly requested resources are returned un-optimized and will not be cached by the Traffic Manager.

The duration, in seconds, resources will be cached on the client’s browser before expiring. This is used as a sliding expiry to set the Expires header, meaning the client will cache the file for the specified number of seconds from when it receives it.

This setting applies only to resources that are optimized and requested by their original URL.

This excludes combined resource sets or resources utilizing URL auto versioning. In these cases the URL of the resource (or resource set) is generated from a hash of the contents, so modifying the Expires header has the effect of altering the resource URL. This means that the resource would have to be re-requested on the strength of the changed URL.