ฟังก์ชั่นอ่านความกว้างของ Scrollbars บน ฺBrowser ของคุณ (Cross browser)

<script type="text/javascript">
  function getScrollBarWidth ()
  {
    var inner = document.createElement( 'p' );
    inner.style.width = "100%";
    inner.style.height = "200px";

    var outer = document.createElement( 'div' );
    outer.style.position = "absolute";
    outer.style.top = "0px";
    outer.style.left = "0px";
    outer.style.visibility = "hidden";
    outer.style.width = "200px";
    outer.style.height = "150px";
    outer.style.overflow = "hidden";
    outer.appendChild (inner);

    document.body.appendChild( outer );
    var w1 = inner.offsetWidth;
    outer.style.overflow = 'scroll';
    var w2 = inner.offsetWidth;
    if ( w1 == w2 ) w2 = outer.clientWidth;

    document.body.removeChild( outer );

    return ( w1 - w2 );
  };
  document.write( 'ความกว้างของ scrollbar คือ ' + getScrollBarWidth() + 'px' );
</script>