function rndImg(imgBase, numPics)
{
  // display a random start image
  var startImgIndex = Math.floor(Math.random() * numPics) + 1;
  changeImg(imgBase, numPics, startImgIndex);
}

function changeImg(imgBase, numPics, index)
{
  // display next images
  var nextImgIndex = Number(index) + 1;
  if (nextImgIndex > numPics)
    nextImgIndex = 1;

  var imgField = document.getElementById("randomImage");
  imgField.src = "images/" + imgBase + nextImgIndex + ".jpg";

  var t = setTimeout("changeImg('" + imgBase + "','" + numPics + "','" + nextImgIndex + "')", 5000);
}

function show(layer)
{
  if (document.getElementById(layer))
    document.getElementById(layer).style.visibility = "visible";
}

function hide(layer)
{
  if (document.getElementById(layer))
    document.getElementById(layer).style.visibility = "hidden";
}

var preloadImages = new Array();
function preloadImg(imgBase, numPics)
{
	if (document.images)
	{
	  for (var i=1; i<=numPics; i++)
	  {
    	preloadImages[preloadImages.length] = new Image();
    	preloadImages[preloadImages.length].src = imgBase + i + ".jpg";
    }
	}
}

function testform()
{
  var valid = true;
  if (document.forms[0].mitglied)
  {
    if (document.forms[0].mitglied.checked == false)
    {
      document.getElementById("mitgliedLabel").className = "checkbox red";
      valid = false;
    }
    else
      document.getElementById("mitgliedLabel").className = "checkbox";
  }
  
	if (!(document.forms[0].email.value != 'name@provider.de' && document.forms[0].email.value != ''))
	{
		document.forms[0].email.value = '';
		document.forms[0].email.focus();
		valid = false;
	}
	
	if (valid == true)
		document.forms[0].submit();
}