var oldvisible = "";
/* Opens and closes Nav Bar Topics.
   'o' is the ID of a div that you want to change. */ 
function toggle(o) {
   var visible;
   /* if we have anything open, close it */
   if (oldvisible != "") {
      document.getElementById(oldvisible).style.display = 'none';
	  document.getElementById(oldvisible + '_img').src = 'tii2009/images/expand.gif';
   }
   /* if the new thing is different, open it, otherwise, leave nothing open */
   if (oldvisible != o) {
	  document.getElementById( o ).style.display = 'block';
	  document.getElementById(o + '_img').src = 'tii2009/images/contract.gif';
   	  oldvisible = o;
   }
   else {
      oldvisible = "";
   }
}