The websites can not be shown properly, other applications works fine, including Safari. So this is only Firefox problem.
3 days ago, Firefox has started to display weirdly. All pages showed diagonally with left side up and right side down. So all the letters are showed on a slant, all images smudged/collapsed. I can not read text and links seem to get out of (original) position.
For example, when I open Gmail and click 'compose' it won't work as the proper link to 'compose' is somewhere else than slanting letters showed 'compose'.
It's hard to explain, I have never had this kind of problem with any applications. Other applications works fine, including Safari works alright. I uninstalled and re-installed Firefox but no good. I still see slanting pages.
Re: The websites can not be shown properly, other applications works fine, including Safari. So this is only Firefox problem.
Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).
Do NOT click the Reset button on the Safe mode start window or otherwise make changes.