var revert = new Array();
        var inames = new Array('nav1', 'nav2', 'nav3', 'nav4', 'nav5', 'nav6', 'nav7', 'nav8', 'nav9');

        // Preload
        if (document.images) {
          var flipped = new Array();
          for(i=0; i< inames.length; i++) {
            flipped[i] = new Image();
            flipped[i].src = "http://theslatefoundation.org/images/"+inames[i]+"_over.jpg";
          }
        }

        function over(num) {
          if(document.images) {
            revert[num] = document.images[inames[num]].src;
            document.images[inames[num]].src = flipped[num].src;
          }
        }
        function out(num) {
          if(document.images) document.images[inames[num]].src = revert[num];
        }