I have a multi select list in a form. All my other controls retain their
values after a post to a new page and the user clicks the Back button on
their browser. However, the list is now blank.

This list is a list that is filled with items as the user creates them and
upon submission of the form, I have JavaScript select all items so that they
are transmitted in the post. The items are transferred correctly to the
Post page. However, upon clicking Back, the list is blank. The single item
select boxes retain their values, the textboxes retain their values. Why
won't this list retain its values?