The cache, or Temporary Internet Files contains a kind of travel record of the items you have seen, heard, or downloaded from the Web, including images, sounds, Web pages, even cookies. Storing these files in your cache can make browsing the Web faster because it usually takes your computer less time to display a Web page when it can call up some of the page's elements or even the entire page from a local folder. But, all those files stored in your cache take up space, so from time to time, you may want to clear out the files stored in your cache to free up some space on your computer. This is called clearing the cache.
While in Firefox, click Tools, Options.
Click Privacy, then click the button Clear to the right of the word Cache.
While in Internet Explorer, click Tools, Internet Options...
On the General tab, in the Temporary Internet Files section, click the Delete Files button.
This will delete all the files that are currently stored in your cache.
Click OK, and then click OK again.