function calc_ecran()
{
	LargeurDecalage = 0;
	hauteurdecalage = 0;
	
	EcranLarg = document.body.clientWidth;
	EcranHaut = document.body.clientHeight;
	
	if (EcranLarg < 772 )
	{
	self.resizeTo(800,600)
	}
	if (EcranHaut < 434 )
	{
	self.resizeTo(800,600)
	}
	EcranLarg = document.body.clientWidth;
	EcranHaut = document.body.clientHeight;
	
	if (EcranLarg > 772 )
	{
		 LargeurDecalage = (EcranLarg-772)/2;
	}
	if (EcranHaut > 434 )
	{
		 hauteurdecalage = (EcranHaut-434)/2;
	}
	
	
}