// cacule la largeur de la fenetre
function GetBodyWidth() {
  var BodyWidth = 0;
  if( typeof( window.innerWidth ) == 'number' ) {
    //Non-IE
    BodyWidth = window.innerWidth;
  } else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
    //IE 6+ in 'standards compliant mode'
    BodyWidth = document.documentElement.clientWidth;
  } else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
    //IE 4 compatible
    BodyWidth = document.body.clientWidth;
  }
  return BodyWidth;
}
// cacule la hauteur de la fenetre
function GetBodyHeight() {
  var BodyHeight = 0, BodyHeight = 0;
  if( typeof( window.innerWidth ) == 'number' ) {
    //Non-IE
    BodyWidth = window.innerWidth;
    BodyHeight = window.innerHeight;
  } else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
    //IE 6+ in 'standards compliant mode'
    BodyWidth = document.documentElement.clientWidth;
    BodyHeight = document.documentElement.clientHeight;
  } else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
    //IE 4 compatible
    BodyWidth = document.body.clientWidth;
    BodyHeight = document.body.clientHeight;
  }
  return BodyHeight;
}
// Positionne le conteneur au millieu
function middle()
{
BodyHeight=GetBodyHeight();
ContHeight=document.getElementById("conteneur").clientHeight;
TopCont=(BodyHeight/2)-((ContHeight/2)+30);
if (TopCont<0)TopCont=0;
document.getElementById("conteneur").style.top=TopCont+'px';
}
middle();

window.onresize = function() {
middle();
}