function apri_popup(url)
  {
   w = 510;
   h = 510; 
   x = (screen.width - w) / 2;
   y = (screen.height - h) / 2;
        
   window.open(url,'','width='+w+',height='+h+',top='+y+',left='+x+',scrollbars=yes');    	  
  }