if (document.body)
{
var larg = (document.body.clientWidth);
var haut = (document.body.clientHeight);
}
else
{
var larg = (window.innerWidth);
var haut = (window.innerHeight);
}
var cote = (larg - 950) / 2;
var marginleft = 950 + cote - 50;
var widthdiv = larg - 950 - cote + 50;

if (widthdiv > 220) {
 widthdiv = 220;
}

$('#headerdroit').css('display','block');
$('#headerdroit').css('left', marginleft);
$('#headerdroit').css('width', widthdiv);