If you posted a link to the page that doesn't display properly in IE9, someone may be able to make a suggestion.
IE9 should render your pages correctly according to the doctype used, but if you continue to see the page render corrrectly only in IE9's compatibiltiy mode, then as a last resort, you can force the browser to use compatibility mode for that page (see here).
What versions of IE does it display correctly on? Do you have a DOCTYPE declaration at the top of your page (in code view)?