function PopPagina(pageURL,Titolo,defaultWidth,defaultHeight){ 
   var PositionX  = (screen.width/2)-(defaultWidth/2);
   var PositionY  = (screen.height/2)-(defaultHeight/2);
   
   if(PositionX<0) PositionX=0;
   if(PositionY<0) PositionY=0;
  
   PopPag = window.open(pageURL,Titolo,'menubar=1,status=1,scrollbars=1,resizable=1,width='+defaultWidth+',height='+defaultHeight+',left='+PositionX+',top='+PositionY);
}