Don’t modify the style.css in wp-content/themes/twentyten
. That leads to much of what used to happen when people would modify the default theme.
Instead, child theme it!
Make directory wp-content/themes/pbear
and create style.css in that directory with just these lines:
/**
* Theme Name: PBear's Rounded TwentyTen
* Description: Rounded Corners for TwentyTen
* Version: 1.0
* Template: twentyten
*/
@import url("../twentyten/style.css");
#wrapper {
margin-top: 20px;
background: #fff;
padding: 0 20px;
/* this?: */
border-radius: 10px;
-webkit-border-radius: 10px;
-moz-border-radius: 10px;
}
Activate that theme and you get TwentyTen with rounded corners. When an update comes out, you won’t have to worry about keeping your changes intact.