With every Internet Explorer release, we’ll get asked about what does IE do this time to break your site. Note, we don’t intentionally attempt to break your site. With every release, we try to make it easier for you to have IE consumers. The goal with this release is to let you have one set of HTML for all the modern browsers without ANY IE specific hacks. We also continue to include our compatibility features like:

• Multiple standards modes, so developers can indicate if they are ready or not for the latest IE9 Standards mode
• Compatibility Button, for consumers that find a site where the developer has not indicated their status and possibly has issues
• Compatibility View List, maintained by IE engineering team, for top sites where the developers have not yet properly indicated their support level

I recently ran across a MSDN resource that has some really good background on changes in IE9. Titled Internet Explorer 9 Compatibility Cookbook, It includes guidance on such topics as:

• Features Changed in IE9

• 20+ issues described

• Features Deprecated in IE9

• A list of DOM events, like attachEvent, detachEvent, createEventObject, fireEvent

• Application Development Guidelines and Tools

• Compatibility View List
• Update Existing Code to Work Across Browsers
• Use Feature and Behavior Detection