function controlBlind(opt) {
	if(opt=='draw') {
		document.write('<div style="position:absolute;left:0px;bottom:0px;width:100%;height:100%;background-color:#E6E6E6;z-index:1" id="blind">&nbsp;</div>');
	}
	if(opt=='erase') {
		//document.getElementById('blind').style.display='none';
		scaleBlind = window.setInterval("controlBlind('diff')", 1);
	}
	if(opt=='diff') {
		with(document.getElementById('blind').style) {
			if(width=='100%') {
				n = 100;
			}
   		n -= 10;
			if(n<=0) {
				window.clearInterval(scaleBlind);
				display='none';
			} else {
				width  = n +'%';
				height = n +'%';
			}
		}
	}
}