function openWindow(url,name,width,height) {
  var x = window.screen.width;
  var y = window.screen.height;
  var left = (x - width) / 2;
  var top = (y - height) / 2;
  var params = "left=" + left + ",top=" + top + ",width=" + width + ",height=" + height + ",toolbar=no,menu=no,statusbar=no,location=no,resizable=no,scrollbars=yes";
  window.open(url,name,params); 
 }

 function openLessons(url,name,width,height) {
  var x = window.screen.width;
  var y = window.screen.height;
  var left = (x - width) / 2;
  var top = (y - height) / 2;
  var params = "left=" + left + ",top=" + top + ",width=" + width + ",height=" + height + ",toolbar=no,menu=no,statusbar=no,location=no,resizable=no,scrollbars=yes";
  window.open(url,name,params); 
 }


 function openPlate(url,name,width,height) {
  var x = window.screen.width;
  var y = window.screen.height;
  var left = (x - width) / 2;
  var top = (y - height) / 2;
  var params = "left=" + left + ",top=" + top + ",width=" + width + ",height=" + height + ",toolbar=no,menu=no,statusbar=no,location=no,resizable=no,scrollbars=no";
  window.open(url,name,params); 
 }