In this article I am going to explain the CSS 3 standard way of achieving rounded corners. Using only this technique is probably not going to give the cross browser behavior that you are expecting.
Border radius properties
It doesn’t matter which way you specify the radius you want for your corners, the browser is going to compute it in four different properties:
1 2 3 4 border-top-left-radius border-top-right-radius border-bottom-right-radius border-bottom-left-radius