The trouble with this is that many websites nowadays use fake fonts where the glyphs are the icons that make up the UI. Without the font, you don't see the icon

The trouble with this is that many websites nowadays use fake fonts where the glyphs are the icons that make up the UI. Without the font, you don't see the icons, and thus have no idea what the various buttons and labels do or mean. It annoys the crap out of me because I'd love to disable fonts for the simple reason that having every page use its own font for text is distracting. I don't need my eyes to adjust to a new font for every page. I want to pick my favorite font and only ever see that one. On a completely unrelated note, I'll never forgive Mozilla for removing support for gopher urls in the browser.