Purpose: 
Keep the item of the current page selected in a menu to indicate visually whis page the visitor is on. 
See an example: the sub-menu on the 'Company' page on the LMSOFT website: http://www.lmsoft.com/company.html

How: 
By inserting a script* in the 'Other HTML & Javascript' tab on all the pages that have the menu in question. 

<script type="text/javascript">
function PinMenu(item)
{
   item.ImageUp2= item.ImageUp;
   item.ImageUp= item.ImageOver;
   item.TagImg.src = item.ImageOver;
}
function UnpinMenu(item)
{
   if (!item.ImageUp2) return;
   item.ImageUp= item.ImageUp2;
   item.TagImg.src = item.ImageUp;
}
var item= FindClassObjectFromId("Menu1_MenuItem1");
PinMenu(item);
</script>

* The names of the items must be replaced in the script by the name of the menu items in Web Creator

The format is always the same: menu name_MenuItemX (X = position in the menu bar starting with 1) ... So if you have a menu called "MainMenu" with 4 items (Home, Information, Products, Contact), the items will be MainMenu_MenuItem1 (for the Home button), MainMenu_MenuItem2 (Information), MainMenu_MenuItem3 (Products) and MainMenu_MenuItem4 (Contact).

The names of the buttons may not follow the order in which they are placed in the menu, but you can check their name in the javascript file menu if needed.

Javascript functions details: 
1. This forces a menu item to use the image 'Over', regardless of the position of the mouse. It also puts aside the original value in order to undo this change. 
function PinMenu(item)
{
   item.ImageUp2= item.ImageUp;
   item.ImageUp= item.ImageOver;
   item.TagImg.src = item.ImageOver;
}

2. This resets the menu to its original condition: 
function UnpinMenu(item)
{
   if (!item.ImageUp2) return;
   item.ImageUp= item.ImageUp2;
   item.TagImg.src = item.ImageUp;
}

This function resets all the root items to their original condition: 
function ResetAllMenuItems()
{
   var menu= FindClassObjectFromId("Menu1");
   for (i=0;i<menu.itemList.length;i++) {
       var item= menu.itemList[i];
       UnpinMenu(item);
   }
}

This portion of code identifies the item to 'pin'. You can insert this code directly in a web object, to secure an item that corresponds to the current page: 
var item= FindClassObjectFromId("Menu2_MenuItem1");
PinMenu(item);

Finally, this script shows how to use a combination of these functions to display items in an iframe for example (or with Show/Hide of elements groups). 
function Menu2_MenuItem1_OnClick()
{
   ResetAllMenuItems();
   GRP_Description.Show();
   var item= FindClassObjectFromId("Menu2_MenuItem1");
   PinMenu(item);
}