var newWindow = null;
   function openWindow(page, name, w, h, r, s){
    var x = (screen.width - w - 40);
    var y = (screen.height - h)/2;
    var specs = "width="+w+",height="+h+",resizable=" +r+",scrollbars="+s+",screenX="+x+",screenY="+y+",left="+x+",top="+y;
    if(newWindow != null){
     if(newWindow.closed){
      newWindow = null;
      newWindow = window.open(page, name, specs);
     }
     else{
      if(newWindow.name != name){
       newWindow.close();
       newWindow = null;
       newWindow = window.open(page, name, specs);
      }
      else{
       newWindow.focus(); 
      }
     }
    }
    else{
     newWindow = window.open(page, name, specs);
    }
   }