When content expiration is enabled, the Web browser compares the current date to the expiration date to determine whether to display a cached page or request an updated page from the server.
To set the expiration of Web site content in IIS 5.0, follow these steps:
In the Internet Information Services snap-in, select the Web site, virtual directory, directory, or file for which you want to set content expiration.
Right-click the Web site, virtual directory, directory, or file and select Properties.
On the HTTP Headers property sheet, select Enable Content Expiration.
Select Expire Immediately, Expire after, or Expire on and enter the appropriate expiration information in the corresponding box.
NOTE: Typically, time-sensitive information is limited to individual files, directories, or Web sites; however, you can also set content expiration for all Web sites on a computer through the configuration of WWW Master Properties.