Firefox Version 3 Beta 4 is now out for testing, and this item from the release notes jumps out:
Memory usage: Several new technologies work together to reduce the amount of memory used by Firefox 3 Beta 4 over a web browsing session. Memory cycles are broken and collected by an automated cycle collector, a new memory allocator reduces fragmentation, hundreds of leaks have been fixed, and caching strategies have been tuned.
What a difference four months makes.
In a quick, unscientific test in a Windows Vista SP1 virtual machine, Firefox version 220.127.116.11 rang up a quick 80 MB of memory when five tabs were used for five different web sites: Youtube, Digg.com's "Spy" page, Channelweb.com, Yahoo mail and Google Docs (that's actually not bad for that version of Firefox.) In that same VM, Firefox version 3 Beta 4 rang up about 60 MB of memory dialing up those same five URLs - - showing that, at first blush, there very well appears to have been some memory improvements added to this rev of Firefox.
Mozilla says the new beta weaves in added malware protection, antivirus integration, simplified add-ons and, in total, about 900 new improvements. But it still needs another round of beta testing and the organization says code freeze for Beta 5 will be on March 18.