function headerChange()
{
  var header_srcs = ['/images/header.jpg',
                     '/images/header2.jpg',
                     '/images/header3.jpg',
					 '/images/header4.jpg',
					 '/images/header5.jpg',
					 '/images/header6.jpg',
					 '/images/header7.jpg',
					 '/images/header8.jpg',
					 '/images/header9.jpg',
					 '/images/header10.jpg']

  var header = new Obj('header_img');


  document.write('<img src="' + header_srcs[Math.floor(Math.random() * header_srcs.length)] + '" width="815" height="311" alt="Center for GeoHazards" />');
}

function Obj(name)
{
  return document.getElementById(name);
}