Blank lines within a PRE are being lost, replaced with simply a newline. For example, there should be a blank line after this line: This could be either in the behaviour of white-space: pre (more likely), or, for all I know (although it's unlikely), in font-family: monospace. See bug 582 for monospace stuff.

Fixed, and I added a regression test for it: mozilla/layout/html/tests/block/pre-lines.html

Verified fixed.