为什么我的显示是这样的呢？
.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;
}
.nav_right
{
width:10px;
background:url(../images/nav_right.jpg) no-repeat;
}
.nav_left,.nav_mid,.nav_right
{
float:left;
height:40px;
}
