hello, can you try to replicate this behaviour when you launch firefox in safe mode once?

Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

Yes, when I launch Firefox in safemode the is still persisting.

please also try to clear the cache & cookies from google.com and reload the page.

also see Websites look wrong or appear differently than they should

I had the same problem in the last two versions of FF for Windows (32bit XP). It turned out I had a minimum font size set in the Advanced settings for fonts & colors on the Content page of Options. Research revealed that FF has trouble with abnormal CSS formatting for minimum font sizes 12 and above. I changed my minimum font size from 13 to 11 and everything works again. This may be a significant problem for people of low vision, since web content as well as smartphone-specific sites are trending toward smaller and smaller fonts to cram more content on a screen. I have normal vision and I only changed the minimum size because I was seeing so many websites with unreadable contract-like small print and I grew tired of having to zoom all the time.

Please update to the current Firefox 23 release.

• Help > About Firefox

• https://support.mozilla.org/kb/update-firefox-latest-version.
• https://support.mozilla.org/kb/Updating+Firefox

The Firefox 20 version that you currently run is no longer supported with security updates.

• It is important to update Firefox and add-ons to the latest version to get all security fixes.

You can use an extension to set a default font size and page zoom on web pages.

• Default FullZoom Level: https://addons.mozilla.org/firefox/addon/default-fullzoom-level/
• NoSquint: https://addons.mozilla.org/firefox/addon/nosquint/