The Expire Web content header (located in common HTTP Response headers) is how IIS determines whether or not to return a new version of the requested web page if the request is made after the web-page content has expired. IIS will mark each web page before it’s sent using the settings you provide for content expiration. The end-user’s browser will translate the expiration mark.
By setting Expire Web content to something other than immediately, you can reduce second-access load times by 50 to 70 percent. This setting will not affect dynamically generated content.
To enable the Expire Web content header (note: this is based on IIS 7.x):
- Launch IIS Manager.
- Navigate to the site that you wish to enable the Expire Web content header.
- Double click on the HTTP Response Headers (located in the IIS grouping).
- In the Actions panel, click on Set common headers…
- Make sure that the Expire Web content is checked.
- Make sure that After is selected.
- Keep the number of days at its default (7).
- Click OK when finished.
