I’m running Firefox 32.0.2 on Fedora 21 and I noticed that sites that use Helvetica look very poorly. Here’s a side-by-side comparison of Firefox and Chrome showing the problem:

I found a lot of complaints online regarding this issue, dating back several years, so I doubt this is a recent bug that will be fixed anytime soon. Luckily there’s a simple fix via Firefox’s userContent.css file.

Go to your Firefox profile directory:

cd ~/.mozilla/firefox/on6byyfm.default/

(replace on6byyfm.default with your profile directory name)

Create a directory called chrome and a file inside that directory called userContent.css:

mkdir chrome
cd chrome
touch userContent.css

Add the following lines to the file:

@font-face { font-family: 'helvetica neue'; src: local('Arial'); }
@font-face { font-family: 'helveticaneue'; src: local('Arial'); }

Restart Firefox and Helvetica fonts will no longer look terrible.

See also: Microsoft’s TrueType core fonts on rpm based systems