for example:
Line 13, Column 1: start tag was here
<LINK REL=stylesheet HREF="css/style.css">
and thats all it says, yet i dont get what is wrong with it, unless its the LINK REL being in upper case.. :/
no, that's
not all it says

the line above says:
"Line 15, Column 7: end tag for "LINK" omitted, but OMITTAG NO was specified "
the line you're reading is saying where it started
i.e. it's saying
- "LINK was opened and not closed" (I'm saying this because the thing it was contained in is now being closed)
- "it was opened here"
Basically you only want to look at error lines, not info lines
you don't need to stick random margin attribute stuff in the body tag because you can just change the margins of the body with CSS (or you could say
style="margin....." in the tag, but since you've got a css page already i'd just use it)
I know you
say it works in major browsers, but have you tested
all versions of those browsers? If it's valid, it's a lot less likely to randomly act wierdly for no good reason. Also, invalid pages get a lower rank on search engines, and if you're going to charge money for this I'd say you're obliged to do the job properly.
Any particular reason you're using frontpage? It was discontinued in 2003 and the sucessor (expression web) is much better