The top left radius property defines the shape of the border of the top-left corner. A higher value creates a more rounded curve.
Value
Description
(numeric)
e.g. '5' would set the top left border radius for an element to 5 pixels (Microthemer automatically adds the 'px' unit if a unit isn't specified). Other commonly used units include 'em' and '%'. So you could enter '5%'.
Top Left Border Radius
The top left radius property defines the shape of the border of the top-left corner. A higher value creates a more rounded curve.
Themeover CSS Reference
Online CSS References: Top Left Border Radius
Online CSS Tutorials: Border Radius