I found this for FF, it's not mine....

Those missing icons are actually supplied by a font that is downloaded from the server (@font-face) as you can see by the little boxes that show the hex code of the characters.

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).

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"