As you may know, Firefox 1.5 is more memory hungry than its predecessor. As Ben Goodger explains this is due to the new flashy back/forward button feature introduced with the 1.5 branch.

The point is that I, practically, never use the Back button but i normally have a LOT of open tabs (up to 20, sometimes). One of this tabs is also always dedicated to Gmail and, I suppose, this is another memory horror beast (now with the chat thing, gmail seems VERY goofy and slow).

If your condition is like mine, I suggest you to “about:config” your browser and disable the back/forward button optimization setting browser.sessionhistory.max_total_viewers to 0.

I really don’t know HOW MUCH does it helps. But now I feel just better :)