arrow = new Image();
arrow.src = "image/arrow.gif";
arrowDown = new Image();
arrowDown.src = "image/arrow_down.gif";

/**
 * Image pair object that is associated to a name.
 */
function ImgPair(name, img1, img2) {
	this.name = name;
	this.img1 = img1;
	this.img2 = img2;
}

function toggleList(e) {
	element = document.getElementById(e).style;
	element.display == 'none' ? element.display = 'block' : element.display='none';
}

function contractList(e) {
	var title = document.title;
	element = document.getElementById(e).style;
	if(title.toLowerCase().indexOf('kurs') == -1) {
		element.display = 'none';
	}
	else {
		element.display = 'block';
		toggleImg(new ImgPair('courseArrow', arrow, arrowDown));
	}
}

function changeImg (name, obj) {
  window.document.images[name].src = obj.src;
}

function toggleImg (imgPair) {

  if(window.document.images[imgPair.name].src == imgPair.img1.src) {
	  window.document.images[imgPair.name].src = imgPair.img2.src;
  }
  else {
	  window.document.images[imgPair.name].src = imgPair.img1.src;
  }
}