For those that want your website to render correctly on IE8, the recent newsletter gave a great example for enforcing IE7 compatibility via a Meta tag. (You can see the new IE logo above)
Per Site Basis:
Site owners and administrators can include the following custom HTTP header to display all pages in Internet Explorer 7 Strict mode for the site:
X-UA-Compatible: IE=EmulateIE7
Per-page basis:
Site owners and administrators can include the following special HTML tag after the <Head> tag on the page:
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7"/>