Windows Server 2003 : Managing WWW Sites (part 4) - HTTP Headers Tab & Custom Errors Tab

HTTP Headers Tab

You can use the HTTP Headers tab of the Properties window for a Web site to enable content expiration on the site, to specify custom HTTP headers that are returned by the server to requesting HTTP clients, to enable and specify Internet Content Rating Association (ICRA) content ratings on the server, and to specify additional MIME mappings for a particular Web site.

Content Expiration

When you enable content expiration on the site and a client browser requests a file from the site, the HTTP headers returned by the server include information regarding the expiration date of the site’s contents. The client can then decide whether it needs to download a newer version of the file or use an existing copy in the client browser cache.

Custom HTTP Headers

This rather esoteric feature allows you to specify custom HTTP headers that are returned by the server to requesting HTTP clients. You might use this option in certain situations involving firewalls or proxy servers to enable or disable specific features during HTTP sessions. You can see the dialog box in Figure 9.

Content Rating

This option is used to enable and specify Internet Content Rating Association (ICRA) content ratings on the server. These settings rate the site’s violence, sex, nudity, and language content and are typically enabled on sites hosting content unsuitable for viewing by minors.

MIME Types

The MIME type option allows you to specify Web site–specific MIME mappings. Click MIME Types and add, edit, or delete the mappings for the current site.

Custom Errors Tab

The Custom Errors tab allows you to specify how your server will generate HTTP error messages when users attempt to access the selected Web site. (See Figure 10.)

The HTTP specification defines that the first header line returned by a Web server in response to a request by a client will contain a number and associated message indicating the status of the request. These three-digit numbers are called HTTP status codes, and they fall within various ranges:

• 200 through 299 A successful HTTP transaction has occurred. (The most common status code is 200 OK.)

• 300 through 399 Redirection to another URL has occurred.

• 400 through 499 An error has occurred. Examples include the following:

  • 400 Bad Request The server can’t understand the syntax of the request.

  • 401 Unauthorized The user’s credentials don’t allow him or her to log on to the server.

  • 403 Forbidden Access is denied for some reason other than user credentials, such as the client having a restricted IP address or needing to use SSL to access the server.

  • 404 File Not Found The file you’re trying to access doesn’t exist (or is misplaced or misnamed) on the server.

• 500 through 599 A server error has occurred or the requested feature isn’t implemented.

Instead of returning bare HTTP status codes and their brief messages for the error codes (400 through 499), however, IIS is configured by default to use predefined HTML pages that contain somewhat more information than the status codes and messages. These “error files” are located in the \%WinDir%\help\iishelp\common folder on the server, and you can modify them if you want.

Alternatively, by selecting one of these error files on the Custom Errors tab and clicking Edit Properties, you can specify that the default HTTP status codes and messages will be returned by the server when that error occurs, or that any specified file located in either a local folder or a network share will be returned when that error occurs. Companies commonly use this feature to create error pages that contain elements such as the company logo, the e-mail address of customer support, or even a search tool for finding the page the client is trying to access.