I am using some jQuery code where I hide a list item...
Hmm that shouldn't happen.
display: none; not
visibility: hidden; or
opacity: 0; (which would hide the element but keep its space occupied).
"This is roughly equivalent to calling .css('display', 'none'), except that the value of the display property is saved in jQuery's data cache so that display can later be restored to its initial value" - from http://api.jquery.com/hide/.
Edit: Have you checked with Firebug (or similar) what actually happens to the element?