Firefox generally looks pretty okay when installing and running it on Windows for the first time. Running it on Ubuntu for the first time however has quite the opposite effect.
So why does Firefox’s font look so crappy in Ubuntu? Well the first problem lies with Ubuntu’s inherent feature of automatically selecting a high screen resolution based on what your monitor can display. Naturally if your screen resolution is set pretty high, then your text is going to be pretty damn small and this would naturally make you whole Firefox experience just that little bit more unpalatable.
So in other words, you could always try changing your screen resolution down for a better effect. The second option you have is of course to change the default fonts that Firefox uses (Edit -> Preferences : General : Fonts & Colors) and select something more pleasing to the eye. Thirdly, you could always just use the ‘Ctrl +’ / ‘Crtl -’ combinations to zoom in or zoom out respectively, thereby controlling how large text appears on screen. (Note that at default, Firefox will zoom everything on the page. You can set this to text only through the settings menu: View -> Zoom : option: ‘Zoom Text Only’)
Oh, and the last thing that you can try is, if you have a TFT display (LCD), is to turn on the subpixel rendering in Ubuntu (System -> Preferences -> Appearance -> Fonts: select ‘Subpixel smoothing (LCDs)’).
Hopefully one of these (or a combination of the lot) works for you. It’s a pity that something as stupid as bad looking fonts turns one completely off from using what is arguably a pretty damn good Internet browser.