function escuchas () {
	
	var esNN4=(document.layers)? 1:0;
	var esIE4=(document.all)? 1:0;
	if (esIE4) {
		var Econtrol=document.getElementById("pantalla").style.visibility;
		if (Econtrol=="hidden") {document.getElementById("pantalla").style.visibility="visible";}
		if (Econtrol=="visible") {document.getElementById("pantalla").style.visibility="hidden";}
		}
	if (esNN4) {
		eval('document.pantalla.visibility="show" ');
		 }
		
	}