function handlePopupClick() {
  window.open(this.href, "mywindow","scrollbars=1,height=750,width=640,left=1100,top=90");
  return false;
}

window.onload = function() {
  var lnks = document.getElementsByTagName('A')
  for(var i = 0; i < lnks.length; i++)
    if(/\bpopup\b/.test(lnks[i].className))
      lnks[i].onclick = handlePopupClick;
}