I noticed that when the Chinese characters are shown in headlines and other places sometimes my browser (Firefox 8 on Windows 7) is mixing and matching fonts in order to fill in the right characters.
This happens because the browser tries to find installed fonts based on what language it suspects the characters are. And for some reason Firefox prefers Japanese to Chinese, thus breaking the rendering of the Chinese characters.
The way to fix this is to specify the language of the text
Otherwise, a webfont might have to be used in order to ensure that a particular client has support for the font in question, but that web font would need excellent coverage of the Hanzi range.
Edit: Some answers seem to suggest that I may be dealing with a faulty set-up. Let me re-iterate:
- I have a default installation of Windows 7 with support for Asian scripts and input methods and have not added or removed any fonts. I also have Microsoft Office 2010 installed which may add some fonts of its own.
- I have a default installation of Firefox and I have not played around with its fonts or css or font-stack settings.
- I have seen this issue with every version of Windows since XP and every version of Firefox since 3.5. Somewhere around the 3.0-3.5 timeframe Firefox changed how they look up fonts and this issue was introduced.
- Different browsers look up Chinese fonts differently. If you don't specify a particular font then you are at the mercy of the browser's language-detection features.
Edit: When Firefox has lang=zh set, the headline font selection is the same as Chrome's:
This looks better but is not perfect in my opinion, because it's using a serif font in a sans-serif headline.
Edit 2: I have verified that this bug still exists in the new Beta theme.