导航栏左右边空白还是没有被撑开？
.nav{
height:40px;
}
.nav_left{
width:10px;
background:url(..images/nav_left.jpg) no-repeat;
}
.nav_mid{
width:980px;
background:url(../images/nav_bg.jpg) repeat-x;
line-height:40px;
}
.nav_right{
width:10px;
background:url(..images/nav_right.jpg) no-repeat;
}
.nav_left, .nav_mid, .nav_right{
height:40px;
float:left;
}
