1) You’re missing a closing ">" on your content div. Add that in and it works fine in ie 6/7 (i copied the code and did it myself and it works / validates)
2) Also, you have no character encoding declared. You need that for it to validate, which is always a good thing to do. Add a standard UTF-8 character encoding by adding "<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>" to the <head> section of your page.
3) Your <img> tag does not comply with xhtml standards as you’ve declared the code to be at the top of your header. It needs a closing forward slash, ie <img src="http://…." alt="something" />
4) Also, your <head> parent tag is not finished. You need a <title> element for it to validate.
5) I should also point out that "overflow-y" doesn’t exist in css 2.1, it does in css 3 though. As css 3 hasn’t been released by the w3c, it won’t validate unless you take that out.
6) I assume you included the css in the xhtml for the purpose of this post, but make sure you include it in a separate file and link it in the head.
I would suggest double checking your urls at the W3C validation service’s website: http://validator.w3.org/
Here’s the code: