Created attachment 733192 [details]
User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:19.0) Gecko/20100101 Firefox/19.0 Iceweasel/19.0
Build ID: 20130220104629
Steps to reproduce:
LWN has an article http://lwn.net/Articles/545741/#Comments
which is named "Schrödinger's
It looks like the bug report was truncated at the UTF-8 character.
The problem is that, with a title with UTF-8 characters (in this case a cat), the title in the tab bar gets truncated without regards to the UTF-8 character boundries. You can see it by visiting the linked LWN page, but that's subscriber-only for the next week, so here is a page that shows the same problem: http://jim.sh/~jim/tmp/ff/857913.html
As the tab size shrinks, you'll see invalid UTF-8 characters at some sizes.
confirming with Firefox20 and Firefox10ESR on windows7
*** This bug has been marked as a duplicate of bug 404856 ***
Created attachment 739754 [details]
Screenshot, Linux: Works when there is enough space
Works on Linux
Firefox 22, self-compiled, 64bit, Ubuntu 12.04 64bit
Of course it works when there's enough space -- we're talking about label truncation here, not normal display.