You can try to disable hardware acceleration in Firefox.

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"

You need to close and restart Firefox after toggling this setting.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can check if there is an update for your graphics display driver and check for hardware acceleration related issues.

• https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

--- Make sure that you allow pages to choose their own fonts.

• Tools > Options > Content : Fonts & Colors > Advanced: [X] "Allow pages to choose their own fonts, instead of my selections above"

You can check the gfx.downloadable_fonts.enabled pref on the about:config page and make sure that it is set to true (if necessary double-click the line to toggle its value to true).

For some reason, this font is a bit ugly on Firefox, even with hardware acceleration enabled (which should improve anti-aliasing). I have attached my sample (not logged in).

If I had to look at this font a lot, I would be inclined to substitute it using a custom style rule. Here are two threads with examples of that:

• https://support.mozilla.org/questions/1089469
• https://support.mozilla.org/questions/1079352?page=4#answer-774249