CSS3 border-radius
To an element to the rounded corners is the "border-radius".
More specifically, it will be in the following description.
div#radius{
width:90%;
height:100px;
background:#FAFAFA;
border:solid 1px #AEAEAE;
border-radius:5px;
}
In the above have put the line, but it can be on the corner round without a line.
In addition, the fine is also possible to specify the like you want to only the upper left corner in the rounded corners.
div#radius{
width:90%;
height:100px;
background:#FAFAFA;
border-top-left-radius:10px;
border-top-right-radius:5px;
border-bottom-left-radius:30px;
border-bottom-right-radius:70px;
}
By using rounded corners, it enables the creation of soft design.
[reference]CSS Reference