It depends. In Firefox, disabling "Allow pages to choose their own fonts" does not completely block web fonts (as setting gfx.downloadable_fonts.enabled to fal

It depends. In Firefox, disabling "Allow pages to choose their own fonts" does not completely block web fonts (as setting gfx.downloadable_fonts.enabled to false would); what it does is to prioritise the default fonts, and move any page-specified fonts to the end of the fallback list. This means that for "normal" text, the browser's default fonts will be used, but if there are Private Use Area character codes that are only supported by the site's custom webfont, it'll still get used for those. So icon fonts that are based on PUA code points will still work. What doesn't work in this scenario is when the icon font doesn't encode its icons in the PUA, but uses normal Unicode characters -- either symbol code points that are supported by the system's default fonts, or as some icon fonts do, regular English words that then use ligature rules to produce the icon glyphs. (So the icon font contains OpenType mappings such as "phone" -> [phone icon].) In this case the content on the page will end up rendered using the default font instead. [Edited: HN doesn't let me include an actual phone icon there, apparently.]