Unfortunately, Firefox has become a huge resource hog. I have to use it everyday under XP and at some point it takes about 1GB of memory + HDD space, goes slower and slower until it can't be operated anymore and needs restarted. Of course, this may also be the fault of certain extensions I have active, but if it wasn't for those, I wouldn't be browsing the Internet nowadays. I have a fixed monthly download quota and can't afford to waste it with useless advertising, Flash and whatnot.
Guys, I'm afraid we need a new browser, designed from scratch for Win9x, that can use HTML5 but can also be able to reject all that advertising that's cluttering the pages. But I already know the answer to that: "keep dreaming..."
The biggest memory bug in Firefox is the history bit, you can get Addins to change how the history works.
Also there is an Addin called "Cache Status" that will let you clear memory and disk cache on the fly, so if you have opened a lot of graphics type web sites and the cache is thrashing as it deletes old stuff for new, you can just click the status bar and clean stuff out.
Also just a thought, but if you have the drive space and ram setting Firefox cache options higher makes a big difference.
You can add in a separate small hard drive(Compact Flash and an adapter to IDE is a cheap and fast swap hard drive. Must be at least twice your available ram, preferably at least three times, or wn9x will have kitties.) as windows swap space and force 9X to use that drive only as swap.
And remember you can put a really big hard drive as storage space on win9x and take all the clutter off the boot drive as long as the controller you use has a 9X driver and maps as a SCSI. You can use upto a 1.5TB SATA as one partition, anything 2TB or higher needs to be partitioned, like the 2.0TB WD Green I got at Christmas time. I had to map the drive as two 1TB partitions or loose a little bit of space, It wasn't much, few hundred meg or so though so depending on what you use the storage for mite make one big partition look good. The drive may have actually been a tiny bit over 2TB as it was a WD AV Green Advanced Format Drive. Now there are some quirks with drives over 750gig(Maybe a problem on a 750gig if lots of small files are on the drive.). Scandisk has memory problems on these big drives, and won't work once the directory gets so big. So you have to fix problems manually or with other apps if a file or directory gets hosed. If you only use the drive as storage and move stuff over to it, you will seldom if ever have any problems. You should not, and probably will not be able, to use these big drives unpartitioned as a boot drive in 9X. Generally add in controllers are not primary controllers anyway. There are cheap PCI SATA controllers with 9x drivers on e-bay. You have to work at it to get cheap drives but there out there.
Anyway a few ideas that mite help.