I've had problems with this Firefox and probably the one before it on two of my three computers for sure, and maybe on the third (I don't remember). There is some problem with style sheets that causes some Web sites to display wrong. For example, opensourcebistro is unreadable, with type running over other type so that it is impossible to read or click on a link. Opensourcebistro isn't the only site with problems. I now use SeaMonkey where I might have used Firefox before unless the site absolutely needs Firefox.
I'm not blaming the package. It may be something in Firefox itself or some interaction with my video drivers or something else. I wonder if anyone else is experiencing this.