On the French login page of gmail, question mark rhombus are shown instead of any accentuated character é, è, ê, à, â. It has been so for a week (I'll pay more attention in the future) and is still the case with r35005.
Confirmed with Safari 3.1.2 and with a local debug ToT, so this is not a WebKit regression, but something that changed on Google side. Steps to reproduce: 1. Log in to your GMail account normally. 2. In settings, change the language to French. 3. Log out. You are brought back to a login page, which has the problem. Re-opening doesn't resolve it. I also see this problem with Spanish, but not with Russian, Ukrainian, Polish, Czech or Catalan. It is not yet clear if this is a WebKit bug, but Firefox works correctly.
Interestingly, the page source does not have this problem.
Created attachment 22109 [details] test case (with .htaccess)
It appears that Firefox has different behavior when seeing unknown charset for the main resource and for subresources. Fort the main resource, it ignores the unknown charset and uses the browser default encoding, while for subresources, it uses Latin-1. WebKit always ignores unknown encoding names (a comment in TextResourceDecoder.app says that it "helps some sites specifying invalid encodings"). We will need to find out what IE does to decide whether to match Firefox here. Regardless, this looks like more of a Google issue than a WebKit one.
<rdar://problem/6056266>
Can you still reproduce this? Looks like this was fixed on Google side. We'd still want to keep this bug open to consider the difference with Firefox though.