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;

}