function getScreenWith(){
  var screenwith = screen.width;
  if (screenwith <= 800){
  }
  else if (screenwith <=1024){
    document.getElementsByTagName("body")[0].style.backgroundImage = "url(fileadmin/templates/images/bg_1024.jpg)";
  }
  else if (screenwith <=1280){
    document.getElementsByTagName("body")[0].style.backgroundImage = "url(fileadmin/templates/images/bg_1280.jpg)";
  }
  else if (screenwith <=1440){
    document.getElementsByTagName("body")[0].style.backgroundImage = "url(fileadmin/templates/images/bg_1440.jpg)";
  }
  else if (screenwith <=1600){
    document.getElementsByTagName("body")[0].style.backgroundImage = "url(fileadmin/templates/images/bg_1600.jpg)";
  }
  else if (screenwith <=1920){
    document.getElementsByTagName("body")[0].style.backgroundImage = "url(fileadmin/templates/images/bg_1920.jpg)";
  }
}