With Firefox 3.6.13 under Linux (ArchLinux) fonts are really jerky. It is really hard for the eyes.
I don't know. The font was holding real still in that picture.
It sounds like in some manner anti-aliasing of fonts isn't set up (or perhaps its just the single font being used by this site?) - I know on my Ubuntu box at home, it doesn't look like that on my Firefox install. Check this blog post for ideas:
http://axcoto.com/blog/tag/firefox-anti-alias
Once again, it may just be the font; that is, for the font being used by the page, the font you have installed is not an anti-aliasing font (and you'll have to figure out how - or if - you can replace it in some manner). Browse the page source, and the CSS to figure out what font is being used (here at my work, IE Dev Tools says it's 'Lucida Grande', Lucida, Verdana, sans-serif). Install something like the firebug and/or web developer plug-ins into Firefox, then attempt to mod the CSS temporarily to only one of the fonts listed for a section in the code, and see if one of them is clearer than the other; if so, then you know that you need to replace (or remove) the "offending" fonts.
Hope this helps...
The problem was with "Lucinda" font family. I made the following style for Firefox Stylish addon an now it is just fine.
@namespace url(http://www.w3.org/1999/xhtml);
@-moz-document url-prefix('http://arduino.cc/forum/'){
* {
font-family: "verdana" !important;
}
}