You can also try:

• Anti-Aliasing Tuner: https://addons.mozilla.org/firefox/addon/anti-aliasing-tuner/

I have the same issue with Helvetica in FF 4.0.1

It renders fine in all other browsers but is showing larger/increased weight in the newest FF.

As Holodyn said, Firefox has always been my baseline for testing, this is a crazy bug even for a beta when your dealing with a browser of this pedigree.

No one can expect their users to install a 3rd party plug-in so a site's font look okay in a brand new browser! The vast majority of the public will not have the technical knowledge to even be able to search for the correct terms to solve this problem, even if they could be bothered in the first place.

Please solve this Mr Firfox

Make sure that you have true type versions of all Helvetica fonts. There are a lot of older bit map versions around that won't work anymore in Firefox 4 and cause Firefox 4 to use a different font, in your case a bold font.

@cor-el - my business partners and I are having this problem on new machines with clean installations of Windows 7 Home Premium and Windows 7 Ultimate. If this is a font issue, it is one that is present by default.

My problems are that some fonts (arial and sans-serif for example) when bolded are a bit wider than on other browsers- especially noticeable (or possibly only) with upper-case.

It seems the problem only happens when "Use hardware acceleration when available" Tools/Options/General is turned "On" (and I assume when hardware acceleration is in fact available). Turning that option off aligns things properly, but that is hardly a "fix".

I have the same issue with weird bold fonts when using Hardware Acceleration. Look at this image I posted in the mozillazine forums during beta a few months ago.

Edit: Actually I posted in in August 2010, so it's more than a few months ago :)

Ok Mozilla - Come On - I just downloaded v5.0 beta and this problem still exists. Do you not have an official comment on this problem?

Am I crazy for needing this resolved? We're not the only firm having this problem!

Do we need a designers petition?
Firefox 4 is rendering at least Arial fonts wrongly.
Please, solve this problem! We can't change all the CSS from all our websites. Google Chome is gaining market share, and it renders quite awesomly, so please, give us users support! You know how hard is to make a website viewable the same way in all the most common browsers...

I don't know if this helps, but I tried some CSS and the problem seems to be this: If you set: "font-family:Arial;" with "font-size" set to:

• "normal" or "100;" to "500;" you get Arial
• "bold;", "bolder;", "600;" or"700;" you get bold Arial
• "800;" to "900;" you get Arial Black
• "bolder;" in a nested element which was in bold Arial you get Arial Black

I'm attaching how I see it with webkit (left) and mozilla(right) (if someone wants, I can copy the code... it's simple but long). Chrome, Safari and Opera render correctly (as we were used to). Chrome and Opera though have strange 600 and 700 weights... Interestingly, Internet Explorer is showing me the same problem that Firefox (are you planning to be bought by Microsoft? Skype was bought and started giving problems... I'm just saying)...

I had this problem with 4.0 thought it would of been resolved by 6.0 but noooooooooooooo I can't read websites with out the arial black font...so I'm either gonna try chrome again or go back to firefox 3.6....For petes sakes fix this firefox

See also:

• Bug 644385 – Arial Narrow, Arial Black fonts do not show on page

(please do not comment in bug reports; you can vote instead)