body { 
  margin:0;
  padding:0;
  background: url(reactive_power_energie_reactive_1600x800.jpg) no-repeat center fixed; 
  -webkit-background-size: cover; /* pour Chrome et Safari */ 
  -moz-background-size: cover; /* pour Firefox */ 
   -o-background-size: cover; /* pour Opera */ 
   background-size: cover; /* version standardisée */ 
   font-family:arial, sans-serif;
   font-size:100%;
   color:#FFFFFF;
}

@media screen and (max-device-width: 480px) {
body {
background: none;
   font-family:arial, sans-serif;
   font-size:100%;
   color:#000000;
}
}