title: jquery: select and unselect items of listbox
body: <p>I have 2 listboxes (select, in HTML) in a ASP.NET page. I want that when one item of list1 is selected, the selected item in list2 is unselected, and viceversa. </p>
  
  <p>The 2 selects are mutually exclusive.</p>
  
  <p>How can I do?</p>