function showGrafik() {

var graf = document.getElementById("grafik-layer");
var tab = document.getElementById("statistik");
var linkan = document.getElementById("rechts-an");
var linkaus = document.getElementById("rechts-aus");

linkaus.style.visibility = "visible";
linkan.style.visibility = "hidden";

graf.style.visibility = "visible";
tab.style.visibility = "hidden";
}

function hideGrafik() {

var graf = document.getElementById("grafik-layer");
var tab = document.getElementById("statistik");
var linkan = document.getElementById("rechts-an");
var linkaus = document.getElementById("rechts-aus");

linkaus.style.visibility = "hidden";
linkan.style.visibility = "visible";

graf.style.visibility = "hidden";
tab.style.visibility = "visible";
}