The suggested CSS is not the right way to modify RadButton. Note that .rbDecoratd class is used to create standard button with rounded corners, which is achieved by using sprite images, and setting background-color will not take affect.
Also changing the height of the button will break the whole button layout. As I mentioned the default button is built with a sprite image which height is 22px, setting higher height will break it.
Alternatively, you could set height of 65 pixels which is also built with sprites: Bigger Icons and Buttons
If you want to use Default style button with different than 22 or 65 pixels, you will need to create your custom sprite and to modify the CSS: RadButton Custom Height Tutorial
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