Apparently spurred by the imminent release of Internet Explorer 8, Microsoft's IE Team has published a list of differences between IE7 and IE8, and how to fix code so that it will work on both: http://blogs.msdn.com/ie/archive/2009/03/12/site-compatibility-and-ie8.aspx
And if you know someone who still (even today) needs proof that the existing IE 7 and below were grossly non-compliant to standards, pass this on to them too.
They don't need to understand HTML or JS or the DOM to appreciate this. This MS blogger is quite honest and upfront about it. Here's a quote; note the repeated use of the phrase "Standards mode", and their recommendation of the "best option in the long run" :-)
We see the majority of compatibility issues in IE8 Standards Mode. Most of these occur when sites expect legacy behavior that no longer exists in IE8 Standards Mode. Upgrading your site to run in IE8 Standards Mode is the best option in the long run, but in the interim you can quickly fix these types of issues by running your site in Compatibility Mode.