The location for cached Firefox web elements is under the \Documents and Settings\[username]\Local Settings\Application Data\Mozilla\Firefox\Profiles\[profilename]\Cache directory in XP, or \Users\[username]\AppData\Local\Mozilla\Firefox\Profiles\[profilename]\Cache in Vista. However the files held there are saved as a range of alphanumeric strings and not as filenames. This is primarily for security purposes, so that a malicious file/script in your cache can't be launched easily. To view the cache contents, type "about:cache?device=disk" (without quotes) in the Firefox address bar and press Enter - all the cached entries will be shown as links, with further details when you click on each link.
