function centrarContenido()
{
	var myWidth = 0, myHeight = 0;
	if( typeof ( window.innerWidth ) == 'number' ) 
	{
		//Non-IE
		myWidth = window.innerWidth;
		myHeight = window.innerHeight;
	} 
	else if ( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) 
	{
		//IE 6+ in 'standards compliant mode'
		myWidth = document.documentElement.clientWidth;
		myHeight = document.documentElement.clientHeight;
	} 
	else if ( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) 
	{
		//IE 4 compatible
		myWidth = document.body.clientWidth;
		myHeight = document.body.clientHeight;
	}

	if ( myWidth < 998 )
	{
		div = window.document.getElementById("contenido");
		div.style.marginLeft = "0px";
		div.style.left = "0%";
	}
	else
	{
		div = window.document.getElementById("contenido");
		div.style.marginLeft = "-499px";
		div.style.left = "50%";
	}
	if ( myHeight < 752 )
	{
		div = window.document.getElementById("contenido");
		div.style.marginTop = "0px";
		div.style.top = "0%";
	}
	else
	{
		div = window.document.getElementById("contenido");
		div.style.marginTop = "-376px";
		div.style.top = "50%";
	}
}

window.onload = centrarContenido;
window.onresize = centrarContenido;