function  popUp(URL,w,h)  {
	x = (screen.width-w) / 2;
	y = (screen.height-h) / 2;
	
	day  =  new  Date();
	id  =  day.getTime();
	eval("page"  +  id  +  "  =  window.open(URL,  '"  +  id  +  "','toolbar=0,scrollbars=1,location=0,statusbar=0,menubar=0,resizable=0,width="+w+",height="+h+",top="+y+",left="+x+"');");
	id.onload = function(){
		id.centrar();
	}
}