Muliti-Lingual Web Sites and Character Encoding?

languageLost asks: "I'm working on developing a multi-lingual web site, and I've come across a major problem. It looks like when web browsers submit a form, they don't include the character encoding they used in the headers anywhere. This means I have no way to distinguish between ISO-Latin-1, Shift-JIS, or GBK, for example. Netscape Navigator, Internet Explorer and Mozilla all have this problem. The browsers do send a header called "Accept-charset", but that's not what I'm looking for (and this header typically lies, in any case). I need to know what encoding was used for the text in the form fields. Does anyone know how to do this without using "detection" heuristics? Why don't the browsers just say what encoding they're using?"