OK so being tired of trying all the complicated steps to speed up firefox.
I found one that works in under 5 easy steps I've tested on three computers and each had a different connection to the Internet.
One being dsl which was hella slow but this proved to work even with it so here goes .
1. Once you've loaded up firefox go to the address bar and type: about:config
2. Right click and select: New @~> Integer
3. Name the integer: nglayout.initialpaint.delay
4. Change the integers value to: 0
hope you like ive been posting my @$$ off lately