var deftop = 0;
var scrtid;
function scroll() {
  clearTimeout(scrtid);
  scrtid = setTimeout('scroll2()',100);
}

function scroll2() {
  if (document.body.scrollTop < deftop) {
    menu.style.top = deftop;
  }
  else {
    menu.style.top = document.body.scrollTop + 12;
  }
}