Implement css markup that support CSS3 "border-radius", "box-shadow" and "linear-gradient" in IE versions 6 to 9
Upload the IE CSS Support plugin to your site, Activate it then check your site on IE browser. That's it! :) You might want to clear your IE browser cache before checking.
Make sure all your "border-radius", "box-shadow" , and "linear-gradien" are in your theme's main stylesheet. Your main style usually named "style.css".
The plugin automatically scan your theme's main stylesheet and look for CSS3 properties to apply the markup. In case you have CSS3 properties in other stylesheet, you can add them. Go to "Settings > IE CSS3 Support".