function writeLine(ln) {
  document.writeln(ln);
}

function showImage() {
  var imageList = new Array();
  
  imageList[0] = 'images/header1.jpg';
  imageList[1] = 'images/header2.jpg';
  imageList[2] = 'images/header3.jpg';
  imageList[3] = 'images/header4.jpg';
  imageList[4] = 'images/header5.jpg';
  imageList[5] = 'images/header6.jpg';
  
  var imageNum = imageList.length;
  
  var theImage = Math.round(Math.random() * (imageNum - 1));
  
  document.write('<img src="'+imageList[theImage]+'" alt="" />');
}