Its actually readable with IE6! It has messed up formatting, but it is quite readable. If anyone is daft enough to use IE6 for their general browsing they are quite used to having sites show up with formatting errors. (we have IE6 to access a couple of ancient applications, but use FireFox for normal browsing).
The formatting errors can be fixed typically quite easily using the following procedure.
Go to settings > writing and select “WordPress should correct invalidly nested XHTML automatically” and then click “save changes.”
Now, starting with your latest post, open it in the editor, make one minor change such as adding and then deleting a space, and then click “update post.” Continue with the rest of the posts that have messed up formatting and wordpress should automatically fix the issues for you.
I was going to use browser shots on the site, but wanted to narrow things down.