function showContent(tabblad,layername){
    var layers  = $(".infoblok");
    var index   = 0;
    while(layers[index]){
        layers[index].style.display = "none";
        index++;
    }
    document.getElementById(layername).style.display = "block";
    var tabbladen = $(".blokmenu a");
        index     = 0;
    while(tabbladen[index]){
        tabbladen[index].className = "";
        index++;
    }
    tabblad.className = "active";
}