I tried this on my Mac and PC and it seems to provide just a little relief. If you recall, Firefox tends to eat memory during browsing, especially if you use a lot of tabs. For each tab, each page will cache several pages back and forward. This is nice if you want speed, but bad if you have several tabs open at once, all active in different Windows. While some said this was a memory leak, Mozilla came out to say it was, in fact, a feature. Well this made it to digg, and now the people have had their say: this may fix your Firefox memory leak. Then again, it might not. It's not a real fix, just a config change. What it does is flush the RAM of stored pages, and move everything to the HD, where large chunks should stay. The author said this saves hundreds of MB at a time. Once you minimize FF, the pages are moved to the HD from RAM. You can then restore FF and see the savings. As you can see from the comments, the mileage you get out of this one varies. The good thing is, it's easily reversible and isn't really hacking Firefox, just twiddling the controls a bit... For more enhancements, there's always the Firefox 1.5 tweak guide.