Reset the page zoom on pages that cause problems: View > Zoom > Reset (Ctrl+0 (zero); Cmd+0 on Mac)

• http://kb.mozillazine.org/Zoom_text_of_web_pages

@cor-el The problem isn't zoom, it's that on many sites the font is displayed as bold when it shouldn't be. I am having this issue, and to test it went and searched on Google. Every word in the search results, buttons, etc is bold. Used Firebug to determine what's not supposed to be bold and there's no difference in the display.

This site is one of them that does not have the issue. Possibly a doctype or charset bug in Firefox 4? (although both Google and this site are !doctype html)

EDIT: It appears that the font Arial is involved. Other fonts might also do this, but Arial appears to always be bold in FF4.0.

Helvetica too. And it looks exactly like Arial.

I found several people mention fixes for this problem, usually involving re-installing the Arial font. This did not work for me.

What did work, at least until Mozilla corrects this issue in an update, was turning off Hardware Acceleration. Go to Tools->Options | Advanced | General tab | Uncheck "Use hardware acceleration when available".

I'm sure this hits performance in some way but so far it is working out fine. Let me know if this works for you guys too.

Yay! At last, a working solution. Spot on: it's Arial and Helvetica that are giving trouble. And just in case: after disabling hardware acceleration, as indicated by Transpar3nt, don't forget you have to restart Firefox to enjoy the workaround!

Yes I am having this issue to with yahoo mail..where did you find the replacement fonts?

I unchecked the hardware acceleration box, and restarted Firefox 4.0. Still have the same problem, I had before. Since upgrading to Firefox 4.0, I can't tell the difference between read and unread mail because instead of unread mail being bold and unread mail being regular text they are identical.

I also tried changing from the default font, but it didn't make a difference.

For the record when I view my mail in Google Chrome the bold and regular fonts for unread and read mail appears as they should. So the problem is definitely a Firefox 4.0 bug.

Update: I tried transpar3nt's workaround. The results were the same: after about the 5th tab that I open is the when the problem begins. The first few tabs are fine, but after that, sans-serif fonts are over-sized and apparently bold. Still wondering why this is happening. It is quite annoying.

Worked for me, to bad firefox now is extremly slow. Takes 10 times as long to load a page. Wich kinda ruins the point of my new internetconnection.

If this is not fixed soon I'll have to go back to internet explorer.

Most people with this problem have a corrupt Arial font (and possibly other fonts). In order to reinstall Arial for Windows 32, download this and simply execute it. In order to reinstall more fonts, check the Corefonts project at Sourceforge.

@kozom

That is not true. This is completely Firefox' fault. Don't blame things on fonts and other nonsense. Bye Firefox, Hello Chrome. Great waste of time to try to fix Firefox every time they update it. They are going the other way, destroying their browser with every new update, very sad.

While it is true that re-installing fonts may be of help to some users, there is another inherent problem with the Firefox browser that I have yet to identify. I have had the problem with fonts displaying in bold, but I have discovered that this only happens in Firefox 4.0.1, 5.o, and 5.0.1 (I have only checked these three). When I re-installed Firefox 3.6.19, the bold fonts were no longer a problem. Everything is displaying just fine.

It should be noted that the fonts are appearing bold in Internet Explorer 9 as well, so while there could be an issue with the newest browsers reading fonts, simply re-installing them is not working. I have not checked Chrome or others yet for the bold font issue.