How set rounded corners in Category Strips?

[najaru]

i have the 3 images,
bg
bg_right
bg_left

i have added in the css additional this code

.navbc {
background: url(images/orangethemeFB/misc/navbcbg.gif) repeat-x;
margin-top: 2px;
margin-bottom: 8px;
}

.navbcright {
background: url(images/orangethemeFB/misc/navbcright.gif) top right no-repeat;
}

.navbcleft {
background: url(images/orangethemeFB/misc/navbcleft.gif) no-repeat;
height: 24px;
padding-top: 9px;
padding-left: 36px;
}

but now i don t find wher apply this style......