The problem was solved changing the font hinting to subpixel (lcd) in font properties under gnome.
** Changed in: firefox (Ubuntu) Assignee: (unassigned) => Keidson Paiva de Freitas Status: Needs Info => Fix Released -- Font is too blurry in firefox interface and pages rendering https://launchpad.net/bugs/67226 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs