var headerImgNum =20;
var headerImgDir = "img/indexheader/";
var headerImgNamePrefix = "header.";
var headerImgNameSuffix = ".jpg";
var headerImgName0 = "header_neu";

headerImg = new Image();

var headerArr = new Array();
var srcArr = new Array();

// initHeaderImg() {

	for (i=0; i<= headerImgNum; i++) {
		theImg = new Image();
		num = (i<10)?"0" + i:""+i;
		name = headerImgNamePrefix + num;
		theImg.src = headerImgDir + name + headerImgNameSuffix;
		theImg.name = name;
		headerArr.push(theImg);
		srcArr.push(headerImgDir + name + headerImgNameSuffix)
	}

// }

headerInx = 0;


function writeHeader() {
	var theSrc;
	headerInx = (Math.round((Math.random()+1) * headerImgNum))%headerImgNum;
	if(headerArr[headerInx])  theSrc = srcArr[headerInx];
	else theSrc = headerImgDir + headerImgName0 + headerImgNameSuffix;
	document.writeln("<img name=\"headerImg\" src=\"" + theSrc + "\" alt=\"Welpen\">");
	if (headerInx < headerImgNum-1) headerInx++;
	else headerInx = 0;
}