Text ecoding showing question marks

I'm not sure if this is just me, or just my browser, but I've checked in several browsers and it still shows up. I'm currently using Shiira, but I've check on Firefox, IE, and Seamonkey and I still get the same problem. I post at a forum that has Japanese characters in it, but when I'm on other pages that don't have Japanese in it, sometimes, there are Chinese characters where there should be apostrophes and if I change the encoding, then it's just a box with a question mark in it or just a question mark. I've tried to go through several browsers to see which would fix the problem, at all, but so far I've gotten nothing, so now I'm thinking that it may be the encoding file on my computer (if there is such a thing). Is anybody getting this problem or does anybody know how to fix it?
neye:

Is your encoding set to UTF Unicode?

Maybe you deleted the japanese & chinese fonts on your system?

I still have them because I can still use them (they're on the list) and I still can see the Japanese kanji, but other characters come up with "?'s".