Shared components used by Firefox and other Mozilla software, including handling of Web content; Gecko, HTML, CSS, layout, DOM, scripts, images, networking, etc. Issues with web page layout probably go here, while Firefox user interface issues belong in the Firefox product. (More info)
This bug is a spin-off from bug 6585, specifically for Unix.
Instead of drawing nothing when a glyph cannot be found for the current char,
we should draw some sort of substitute. See bug 6585 for the solution Roger
came up with for Windows.