var changed = 0;
var todo = window.setInterval(function() { handleBottomBG(); }, 500);

function handleBottomBG() {

  if(changed != 1) {
    if(document.getElementById("english")) {
      document.getElementById("main_bottom_bg").style.backgroundImage = "url(fileadmin/img/layout/bg_main_bottom_en.png)";
      changed = 1;
    }
    if(document.getElementById("chinese")) {
      document.getElementById("main_bottom_bg").style.backgroundImage = "url(fileadmin/img/layout/bg_main_bottom_ch.png)";
      changed = 1;
    }
  }

  return true;
}