.bg_move
{
position:absolute;
top:160px;
left:50%;
margin-left:-800px;
width:1600px;
height:1000px;
background: url('/images/bg/0006.jpg') no-repeat;
z-index:-1;
opacity:0.5;
}

.bg_fixed
{
position:fixed;
top:200px;
left:50%;
margin-left:-800px;
width:1600px;
height:1000px;
background: url('/images/bg/0006.jpg') no-repeat;
z-index:-1;
opacity:0.5;
}