BODY 
{
position:absolute;
background-color:RGB(255,255,255);
margin:0px;
padding:0px;
height:100%;
width:100%;

}
.bloc
{
height:646px;
width:870px;
margin:0px;
padding:0px;
margin-left:0px;
margin-right:0px;
vertical-align:top;
text-align:center;
background-image:url("intro1.jpg"); 
background-repeat:no-repeat;
}