var lastCurrent = 0;
$(document).ready(function(){
   $("#header ul li a").click(function(){
       var index = $("#header ul li a").index($(this));
       clickNavButton(index);
   });
});

function clickNavButton(index)
{
  $($("#header ul li a")[lastCurrent]).removeClass('current');
       $($("#header ul li a")[index]).addClass('current');
       lastCurrent = index;
       
       goToSlide(index, $("div.glassWrapper"), $("div.outterWrapper"));
}

function goToSlide(index, glass, slipper)
{
 if(navigator.appName != 'Microsoft Internet Explorer')
 {
  glass.css("display", "block")
    .animate({"opacity":"1"}, 300, "swing", 
      function(){
        slipper.stop()
          .animate({"left":(index * -960).toString() + "px"}, 500, "swing",
            function(){
               $("div.glassWrapper").animate({"opacity":"0"}, 300, "swing",
                 function(){
                   $("div.glassWrapper").css("display", "");
                 });
            });
      });
 }
 else
 {
   slipper.stop().animate({"left":(index * -960).toString() + "px"}, 500, "swing");
 }
}