From MozillaZine Knowledge Base
When a page is loaded, it is cached so it doesn't need to be downloaded to be redisplayed. For e-mail and news, messages and attachments are cached as well. This preference controls the maximum amount of hard drive space to use for caching purposes.
Possible values and their effects
Do not cache files on the hard drive.
Any positive integer
Maximum amount of hard drive space in KB to use for cache. (Firefox default: 50000. Default for OpenVMS systems: 4096. Default for all others: 51200)
Tools -> Options -> Advanced -> Network / Offline Storage (Firefox 3)
Tools -> Options -> Advanced -> Network & Disk Space (Thunderbird 3)
Mozilla Suite and SeaMonkey
Edit -> Preferences -> Advanced -> Cache
First checked in
Present since at least 2000-10-30. Exact checkin date unknown.
Has an effect in