window.onload = function (){
	if (document.getElementById('theLayer')) {
		var w = 0;
		var h = 0;
			//IE
		if(!window.innerWidth) {
			//strict mode
			if(!(document.documentElement.clientWidth == 0)) {
				w = document.documentElement.clientWidth;
				h = document.documentElement.clientHeight;
			}
			//quirks mode
			else {
				w = document.body.clientWidth;
				h = document.body.clientHeight;
			}
		}
			//w3c
    	else {
				w = window.innerWidth;
				h = window.innerHeight;
			} 
			var browserbreedte = Math.floor(w);
			var layerbreedte = Math.floor(document.getElementById('theLayer').style.width.replace('px',''));
			var positielinks = Math.floor((browserbreedte / 2) - (layerbreedte / 2));
		document.getElementById('theLayer').style.left = positielinks + 'px';
		document.getElementById('theLayer').style.visibility = 'visible';
	}
}
function layer_sluiten(){
	document.getElementById('theLayer').style.visibility = 'hidden';
}