For web designers and some of those who are trying out IE9, especially since the release of IE9 RC today, you might want switch IE9 into Compatibility View. Most people say to press F12 and then select Compatibility View. However, if you do it this way you will lose this setting once you close and re-open your browser. Here are the steps for enabling Compatibility View in IE9 and saving it for certain sites.
Enable Compatibility View in IE9
Press the ALT key on your keyboard to make the hidden file menu at the top of IE9 viewable.
Click the “Tools” menu and select “Compatibility View Settings.”
Type the name of the site you want do add and hit “Add.” You can see in my example, I added perkstreet.com, because I noticed some of their menus don’t display yet in IE9 and so I want it to run in Compatibility View. Also, the bottom option can also be checked if you want everything to run in Compatibility View.
These settings will be saved when you close your browser.