IE9 uses Quirks mode but this is an easy fix:
Use <!DOCTYPE html> and add
<meta http-equiv="X-UA-Compatible" value="IE=9"> to the <head> section of your HTML page. It will force Internet Explorer to use IE standards mode.
(taken from http://stackoverflow.com/questions/...s-compliant-mode-when-developing-on-localhost)
Apart from the rounded corners it looks alright in IE when it uses the correct rendering mode.
Also, it doesn't look like you've used <HTML></HTML> tags? Unless the View Source utility in Chrome is hiding them.
If I may make a small suggestion: I'd recommend changing the displayed username that's shown in the blog posts to something other than Admin