I just opened Firefox and all of a sudden some sites have started showing Chinese characters. Refresh doesn't seem to help. Can anyone tell me what's going on?
Here's the screenshot:
It's showing the same way in Google Chrome.
The web site http://diveintohtml5.com (currently) appears to show a partial Chinese translation of the book, just like your screenshot.
I don't think this is a problem you can fix.
Go to Tools->Options->Content tab. Check your default font, then click Advanced on the Default Fone line and make sure you default encoding is correct (mine is Western ISO-88591-1).
Finally, and this may be whats messed up: in the Content tab at the bottom there is a Language section. Click the Choose button and make sure English/United States [en-us] is first. (or w/e your country is)