var currImg = 1;

function animateBackground() {
  var divClassName = "content_startseite";     
  var currClassName = document.getElementById("news_container").className;    
  var newClassName = divClassName + currImg++;
  document.getElementById("news_container").className = newClassName;
  
  if (currImg <= 5) {
  
  } else {
    currImg = 1;
  }
      
  setTimeout("animateBackground()",5000);  
}