var timer;
    
    function nextTab() {
        if ($('div > .home-tab-active').next().html() !== null) {
            //toggle right column
            $('div > .home-tab-active').next().toggleClass('home-tab-active');
            $('div > .home-tab-active:first').toggleClass('home-tab-active');
            //toggle left column
            $('div > .stappen-actief').next().toggleClass('stappen-actief');
            $('div > .stappen-actief:first').toggleClass('stappen-actief');
        } else{
            //toggle right column
            $('div > .home-intro:first').toggleClass('home-tab-active');
            $('div > .home-intro:last').toggleClass('home-tab-active');
            //toggle left column
            $('div > .stappen:first').toggleClass('stappen-actief');
            $('div > .stappen:last').toggleClass('stappen-actief');
        }
        //reset timer
        timer = null;
        //set timer
        timer = setTimeout("nextTab()", 4000);
    };
    
    $(function(){
        //hovermenu
        $('.stappen').mouseenter(function() {
            $('.stappen-actief').toggleClass('stappen-actief');
            $('.home-tab-active').toggleClass('home-tab-active');
            
            $(this).toggleClass('stappen-actief');
            
            var stap = '.' + $(this).attr('rel');
            $(stap).toggleClass('home-tab-active');
        });
        
        //stoptimer on mouseover
        $('#left, #right').mouseover(function() {
            clearTimeout(timer); 
        });
        //set timer on mouseleave
        $('#left, #right').mouseleave(function() {
            timer = setTimeout("nextTab()", 3000);
        });
        timer = setTimeout("nextTab()", 3000);
    });