It can be important to expire pages because browsers have something known as a cache, a space on the hard drive where they store pages of web sites you have visited. If you go back to a site you have already visited, the browser can load some or all of the page from the cache rather than having to retrieve the whole page again.
Here you can see a < meta > tag that will cause the page to expire on Sunday, April 16, 2010, at 11:59 (and 59~seconds) p.m. Note that the date must follow the format shown.
< meta http-equiv=”expires” content=”Sun, 16 April 2010 23:59:59 GMT” />
If this were included in a document and the user tried to load the page after the expiry date, then the browser would not use the cached version; rather it would try to find a fresh copy from the server. This helps ensure that users get the latest copies of documents and thereby prevents people from using outof- date information.
Preventing a Browser from Caching a Page:
You can prevent some browsers from caching a page altogether using the value pragma for the http-equiv attribute and a value of no-cache for the content attribute like so:
< meta http-equiv=”pragma” content=”no-cache” />
Unfortunately, Internet Explorer 4 and later versions ignore this rule and cache the page anyway.
