From MozillaZine Knowledge Base
Firefox 2.0 introduces a built-in Session Restore feature, allowing the user to continue browsing from where they left off if browser restarts. This preference controls how much POST data will be stored per history entry as part of the stored session.
Possible values and their effects
No limit on amount of stored POST data
Do not store POST data in saved sessions (default)
(any positive integer)
Store this many bytes’ worth of POST data per saved history entry in saved sessions.
Saving POST data in the saved session can result in unwanted behavior in certain situations; for example, loading a saved session could potentially re-send an email or re-submit an online order. If you set this preference to anything other than 0, you may want to also keep browser.sessionstore.privacy_level set to 1.
First checked in
Has an effect in