En lille smule JQuery

JScript kode 

 $(document).ready(function(){
     var vari = $(this).attr('name');
     $('.nav_btn.current').animate({left: 0}).removeClass('current');
     $('.nav_btn').click(function(){
         $(this).animate({left:'50%'}).addClass('current');
     });
 });

JScript kode 

 var lastButton = undefined;
 
 $(document).ready(function(){
     $('.nav_btn').click(function(){
         if(lastButton != undefined){
             $(lastButton).animate({'left':'0%'});
         }
         $(this).animate({left:'50%'});
         lastButton = this;
     });
 });