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<html><head></head><body><form name="myform"><select name="software">  <option value="1" onFocus="filterOS()">OS</option>  <option value="2" onFocus="filterGames()">Games</option></select><br><select name="submenu">  <option value="1"></option>  <option value="2"></option></select><br><script>function filterOS(){document.myform.software.options.length=0;document.myform.software.options[0]=new Option("linux")document.myform.software.options[1]=new Option("mac")}function filterGames(){document.myform.submenu.options.length=0;document.myform.submenu.options[0]=new Option("bzflag")document.myform.submenu.options[1]=new Option("tuxtype")}</script><input type="submit" name="submit"></form></body></html>