Can I get away with testing sites using IE8 with IE7 compatibility on?

Question

As a developer, can I safely upgrade to IE8 and use its IE7 compatibility mode to test how sites look in IE7? For IE6, I have a virtual machine and it is quite inconvenient. I don't want to upgrade to IE8 and then have another virtual machine now for IE7.

Or is IE7 compatibility mode really different and I can't rely on that?

Answer 1

Compatibility mode in IE8 is not a 100% emulation of IE7. Security changes were not versioned, and some DOM operations were not versioned. Check out this blog post form Microsoft for a list of changes.

http://blogs.msdn.com/ie/archive/2009/03/12/site-compatibility-and-ie8.aspx