.nav_left
{ 
left:0;
position:absolute; 
height:100%; 
width:20%;
z-index:100; 
outline:none;
cursor:pointer;
background: transparent url(/img/left.gif) no-repeat scroll left center;
}

.nav_right
{
right:0; 
position:absolute; 
height:100%; 
width:20%;
z-index:100; 
outline:none;
cursor:pointer;
background: transparent url(/img/right.gif) no-repeat scroll right center;
}