$(document).ready(function() {
 $("ul#topnav li").hover(function() { //Hover over event on list item
      $(this).css({ 'background' : '#1376c9 url(topnav_active.gif) repeat-x'}); //Add background color and image on hovered list item
      $(this).find("span").show(); //Show the subnav
      } , function() { //on hover out...

      $(this).css({ 'background' : 'none'}); //Ditch the background
      $(this).find("span").hide(); //Hide the subnav
      });
});