5.4. More Than Just Images

Using a far future Expires header on images is fairly common, but this best practice should not be limited to images. A far future Expires header should be included on any component that changes infrequently, including scripts, stylesheets, and Flash components. Typically, an HTML document won't have a future Expires header because it contains dynamic content that is updated on each user request.

In the ideal situation, all the components in a page would have a far future Expires header, and subsequent page views would make just a single HTTP request for the HTML document. When all of the document's components are read from the browser's cache, the response time is cut by 50% or more.