Hello,

I have a WebDataMenu inside of a tab of an AjaxControlToolkit TabContainer, with a few WebImageButtons arranged horizontally. The page renders correctly in IE9, Chrome, etc, but when I switch my IE to IE8 mode and IE8 standards, I see a javascript error in some of the javascript code, in a function named __resizeListItems (line 468 is bolded and underlined):

Line: 468
Error: Invalid argument.

__resizeListItems:function(item)
{
   /* 2010-02-18 Bug#16534 - get the group height and go resize inner LI's 
    * do not set line-height accordingly, eventhough it is the only way
    * to make texts appear aligned vertically.
    * setting line-height will propaged throughout the children which is not desired!
    */
   var group = this.get_element().getElementsByTagName("UL")[0];
   if(!$util.isNullOrUndefined(item))
   {
       group = item._get_subgroup();
   }

   var childItem = this.getItems().getItem(0);
   var grpSettings = this._menuGroupSettings;
   if(!$util.isNullOrUndefined(item))
   {
       childItem = item.get_childItem(0);
       grpSettings = item.get_itemsGroupSettings();
   }

   if($util.isNullOrUndefined(childItem) || $util.isNullOrUndefined(grpSettings))
       return;

   if(grpSettings.get_orientation() == $IG.Orientation.Vertical)
       return;

   if(childItem._element.style.height != "" || childItem._element.style.height.length > 2) return;

   var MaxHeight = 0;
   var nChildItem = childItem;
   while(nChildItem != null)
        {
            if(!nChildItem.get_isSeparator())
            {
                (nChildItem._element.offsetHeight > MaxHeight) ? MaxHeight = nChildItem._element.offsetHeight: null;                    
            }
            nChildItem = nChildItem.get_nextItem();
        }

   if(childItem != null)
   {
     MaxHeight -= $util.toIntPX(null, 'paddingBottom', 0, childItem._element);
       MaxHeight -= $util.toIntPX(null, 'paddingTop', 0, childItem._element);
       MaxHeight -= $util.toIntPX(null, 'borderTopWidth', 0, childItem._element);
       MaxHeight -= $util.toIntPX(null, 'borderBottomWidth', 0, childItem._element);
       MaxHeight -= $util.toIntPX(null, 'marginBottom', 0, childItem._element);
       MaxHeight -= $util.toIntPX(null, 'marginTop', 0, childItem._element);
       MaxHeight -= $util.toIntPX(null, 'paddingBottom', 0, group);
       MaxHeight -= $util.toIntPX(null, 'paddingTop', 0, group);
       MaxHeight -= $util.toIntPX(null, 'borderTopWidth', 0, group);
       MaxHeight -= $util.toIntPX(null, 'borderBottomWidth', 0, group);
       MaxHeight -= $util.toIntPX(null, 'marginBottom', 0, group);
       MaxHeight -= $util.toIntPX(null, 'marginTop', 0, group); 
   }

        while(childItem != null)
        {
            if(!childItem.get_isSeparator())
            {
                childItem._element.style.height = MaxHeight + 'px';                    
                //childItem._element.style.lineHeight = groupHeight + 'px';                    
            }
            childItem = childItem.get_nextItem();
        }
},