var aktiv = window.setInterval("LogoScrolling()", 20);

function LogoScrolling() {
  var cont1 = document.getElementById("logo_1");
  var cont2 = document.getElementById("logo_2");
  if (!cont1 && !cont2) {
    window.clearInterval(aktiv);
  }
  else {
    var breite = cont1.style.width;
    var left1 = cont1.style.left;
    var left2 = cont2.style.left;
    breite = breite.replace(/px/g, "");
    left1 = left1.replace(/px/g, "");
    left2 = left2.replace(/px/g, "");
    left1 -= 1;
    left2 -= 1;
    if ((parseInt(left1) + parseInt(breite)) <= 0) {
      left1 = breite;
    }
    if ((parseInt(left2) + parseInt(breite)) <= 0) {
      left2 = breite;
    }
    cont1.style.left = left1 + "px";
    cont2.style.left = left2 + "px";
  }
}

function LogoScrollOff() {
  window.clearInterval(aktiv);
}

function LogoScrollOn() {
  aktiv = window.setInterval("LogoScrolling()", 20);
}