Yes, maybe it is only on the Mac, I can't seem to replicate it on Windows 7. Firefox has a dotted selection outline that can appear around selected items (e.g., tab around the page and you will see it around links). Does the hairline look like that, or is it solid? --- If it affects a site you maintain, consider querying the [http://forums.mozillazine.org/viewforum.php?f=25 mozillaZine Web Development board]. Separate forum, separate registration. Please note the tips in the Sticky Post at the top of the forum before posting.