code: function firstTabbable(node, allowFocusable) {
  		var tabIndex = _getTabIndex(node);
  		if ((tabIndex >= 0 || allowFocusable && tabIndex >= -1) && !node.disabled && node.offsetParent && window.getComputedStyle(node).visibility === "visible") {
  			return node;
  		}
  		if (node.hasChildNodes()) {
  			for (var i=0; i<node.childNodes.length; i++) {
  				var result = firstTabbable(node.childNodes[i]);
  				if (result) {
  					return result;
  				}
  			}
  		}
  		return null;
  	}
docs: /*
  Inspired by http://brianwhitmer.blogspot.com/2009/05/jquery-ui-tabbable-what.html