We use progressive enhancement for some visual features, such as rounded corners, which means they will appear in browsers that support the border-radius CSS property (IE9).
With regard to the missing icons, it looks like the sprite images that holds all icons has not been loaded, but the reason for this is not clear. You can inspect the elements that should have a background image icon with IE's web developer toolbar to see what's wrong. If you need further assistance, please open a new support ticket and attach a runnable demo there.
the Telerik team
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