Getting Intimate with Elements - Head First HTML and CSS - page 388

Specifying Border Corners
You can create rounded corners on all four corners,
or just one corner, or any combination.
You can specify all four corners with one number.
border-radius: 15px;
Or you can specify each corn er
separately. Notice that you c an use
px or em to specify the radi us size.
border-top-left-radius: 3em;
border-top-right-radius: 3em;
border-bottom-right-radius: 3em;
border-bottom-left-radius: 3em;
border-top-left-radius: 15px;
border-top-right-radius: 0px;
border-bottom-right-radius: 0px;
border-bottom-left-radius: 15px;