$(document).ready(function() {
  $("ul#topnav li").hover(function() { //Hover over event on list item
       //$(this).css({ 'background' : '#638d22 url(menu_hover.gif) repeat-x'}); //Add background color and image on hovered list item
       $(this).css({ 'background' : '#638d22'}); //Add background color and image on hovered list item
       //$(this).css({ 'height' : '36px'}); //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
       });
});