Default Encoding and Unreadable Characters

[nyjyeh]

Hi~ Can somebody help me?

There are some Chinese characters on my Shop Cart web pages.
(ex:http://www.confidenceusa.com/site/store-fish-oil.php, then please click "ADD TO CART"; then you will see some Chinese characters became UNREADABLE characters, but some Chinese characters show correctly. Same problem happen at the following couple pages as well as in the receipt page)

I checked the source code on those pages and found that the default encoding is "charset=ISO-8859-1" , so I am just wondering whether I can edit it to "charset=UTF-8" ???