function katLayer(what) {
	if (what=='show') {
		document.getElementById('myoverlayer').style.left = (window.innerWidth/2);
		document.getElementById('myoverlayer').style.top = (window.innerHeight/2);
		document.getElementById('myoverlayer').style.display='block';
	}
	else if (what=='hide') { document.getElementById('myoverlayer').style.display='none'; }
}