UT8 or Unicode is designed to represent all the characters for all the languages in the world. So theoretically means that you can use it to display any language that you can think of using that character encodiing system.

The two main character encoding for chinese characters are gb2312 for simplified chinese(used in Mainland China) and Big 5 for traditional chinese (used in Taiwan).

The chinese input used in Windows 2000 and above uses gb2312 for simplified chinese and Big 5 for traditional chinese so there's no way to enter UTF8 by default. Better stick to gb2312 or Big 5 for a chinese web site at the moment.

How exactly are you entering UTF8 for chinese characters into your database?

There's two places where this thing could go wrong. During entry and during output. If you enter the text as something other than utf-8 and you specify utf-8 as the charset to use, you won't be able to see the page correctly.
The other scenario would be the text is entered as utf-8 and using the wrong charset in the html file. Since this one would be solved by the solution given in the second post, this is probrably not the case.
Without knowing how the data is entered into the system, it's hard to determine where exactly the system went wrong.