function centrar(url, titulo, height, width) {
	var str = "height=" + height + ",innerHeight=" + height;
	str += ",width=" + width + ",innerWidth=" + width;
	
	var ah = screen.availHeight - 30; 
	var aw = screen.availWidth - 10; 
	var xc = (aw - width) / 2;
	var yc = (ah - height) / 2;

	str += ",left=" + xc + ",screenX=" + xc;
	str += ",top=" + yc + ",screenY=" + yc;         
	
	window.open(url, titulo, str);
 }
 
 function centrarconscroll(url,titulo,height,width){
	
    var str = "height=" + height + ",innerHeight=" + height;

    str += ",width=" + width + ",innerWidth=" + width;

    var ah = screen.availHeight - 30;

    var aw = screen.availWidth - 10;

    var xc = (aw - width) / 2;

    var yc = (ah - height) / 2;

	str += ",left=" + xc + ",screenX=" + xc;

	str += ",top=" + yc + ",screenY=" + yc + ",scrollbars = 1";
                     
	window.open(url,titulo,str);

 }