function openNewWindow(url,Wwidth,Wheight) {
var screen_height = screen.height;
var screen_width = screen.width;
newWindow=window.open(url, 'mywindow', 'scrollbars=no,status=no,width=' + Wwidth + ',height=' + Wheight + ',screenX=' + (screen_width-Wwidth)/2 + ',screenY=' + (screen_height-Wheight)/2 + ',top=' + (screen_height-Wheight)/2 + ',left=' + (screen_width-Wwidth)/2 + '');

   // Permet de retrouver le focus lorsque dj ouvert
  if(newWindow.focus){newWindow.focus();} 
 }