function central()
{
var wid = document.body.clientWidth;
	var left_pos = parseInt(wid - 630)/2;

 
	document.getElementById('middle1').style.left = (left_pos + "px");
	document.getElementById('middle2').style.left = (left_pos + "px");
	document.getElementById('middle3').style.left = (left_pos + "px");
	document.getElementById('middle4').style.left = (left_pos + "px");

}

function scrolldown()
{window.scrollBy(200,760);
}