/*html { 
  top:-100px;
  margin:0;
  padding:0;
  background: url(../img/fond.png) no-repeat center fixed; 
  /*background-size: cover; /* version standardisée 
}
*/
#header
{
top:0; left:0; right:0;
position:absolute;
width:100%;
height:70px;
z-index:9999;
/*border-bottom:1px solid black;*/
}

#contenu
{
top:-70px; left:0; right:0;
position:absolute;
width:100%;
z-index:999;
/*border-bottom:1px solid black;*/
}

#about
{
top:600px; left:0; right:0;
position:absolute;
width:100%;
background-color:#ffffff;
z-index:9999;
/*border-bottom:1px solid black;*/
}