var newwindow;
function poppaa(url) {
  
  var leveys = 425;
  var korkeus = 800;
  var vasen = screen.width - screen.width/2 - leveys/2;
  var yla = screen.height - screen.height/2 - korkeus/2;

  newwindow=window.open(url,'nimi','height='+korkeus+',width='+leveys+',left='+vasen+',top='+yla+',resizable=no,scrollbars=yes');
  if (window.focus) {newwindow.focus()}
}