Which web browser, out of curiousity?
The Greek letters, etc., look fine on my Sony, and in ADE, and on Stanza on a friend's iPhone, but I have had trouble with them not appearing right in calibre's viewer. I assumed it was a fault with calibre's viewer. I asked Kovid about it
here -- I wonder if this is the cause. I'll do some investigating. Thanks.
EDIT: No, this doesn't seem to be the cause of the trouble I was having with Greek letters. I tried removing the ISO-... tag, and still got the problem with Greek letters in calibre.
If I just open one of the html parts in a browser, the non-ASCII is broken too, at least until I change the encoding to UTF-8 on my Browser. But apart from the one mentioned above (which seems only to apply to Greek, not emdashes and smart quotes, etc.), I haven't had any trouble with actual ePub viewers. Still it's probably safer to get rid of the confusing extra tag in there.