function popup(f,scrol,menu,l,a) {
var i = (screen.width - l)/2;
var j = (screen.height - a)/2;
  window.open(f,'janela_nova','resizable=yes,scrollbars='+scrol+',menubar='+menu+',height='+a+',width='+l+',top='+j+',left='+i);  
}