Detect Scrollbar Widths

<?php
function getScrollbarWidth() {
  var sBarWidth = 0;
  var scr = null;
  var inn = null;

  if (is_ie) {
    // create form
    scr = document.createElement('form');

    // move form off screen so no one can see it
    scr.style.position = 'absolute';
    scr.style.top = '-1000px';
    scr.style.left = '-1000px';

    // create a text area
    inn = document.createElement('textarea');

    //set id so we can grab it later
    inn.setAttribute('id', 'ta');

    // add textarea to form
    scr.appendChild(inn);

    // add the element to the document
    document.getElementsByTagName("body")[0].appendChild(scr);

    // grab the text area by id
    var tarea = fetch_object('ta');

    // turn scroll bars off
    tarea.wrap = 'off';

    // get height
    sBarWidth = tarea.offsetHeight;

    // turn scroll bars on
    tarea.wrap = 'soft';

    // get difference
    sBarWidth -= tarea.offsetHeight;
  } else {
    var wNoScroll = 0;
    var wScroll = 0;

    // Outer scrolling div
    scr = document.createElement('div');

    // move form off screen so no one can see it
    scr.style.position = 'absolute';
    scr.style.top = '-1000px';
    scr.style.left = '-1000px';

    // set binding height and width
    scr.style.width = '100px';
    scr.style.height = '50px';

    // Start with no scrollbar
    scr.style.overflow = 'hidden';

    // Inner content div
    inn = document.createElement('div');
    inn.style.width = '100%';
    inn.style.height = '200px';

    // Put the inner div in the scrolling div
    scr.appendChild(inn);

    // Append the scrolling div to the doc
    document.body.appendChild(scr);

    // Width of the inner div sans scrollbar
    wNoScroll = inn.offsetWidth;

    // Add the scrollbar
    scr.style.overflow = 'auto';

    // Width of the inner div width scrollbar
    wScroll = inn.offsetWidth;

    // Pixel width of the scrolbar
    sBarWidth = (wNoScroll - wScroll);
  }

  // Remove the scrolling div from the doc
  document.body.removeChild(document.body.lastChild);

  return sBarWidth;
}