Ok. Here is firefox tweak for 128 MB or less RAM:
http://users-guide.org/index.php?c=text&id=75
Also you should take a look at:
http://kmeleon.sourceforge.net
K-Meleon is superb browser for older computers like Pentium 1 and Pentium 2. Freeware. Opensource. I just tested it and i like it.