It's the copyright symbol near the bottom. Try using the entity "©" instead of the symbol.
(If you have a text editor that shows line numbers (I use
Notepad++), that sometimes helps interpret the validator feedback. For this page, the validator said the bad character was on line 80, but I think that was a couple lines off.)
Edit: Also, I think the IE problems are related to the use of positioning in the stylesheet. One way to debug this is to go back to a blank stylesheet (both mystyle.css and the CSS in the head section) and add items back to the stylesheet one at a time, in order to see the individual effects of each change.