window.onload = getSrc;

function getSrc()
{
  var x = document.getElementsByTagName('a');
  for (var i=0;i<x.length;i++)
  {
    if (x[i].getAttribute('className') == 'changeImg' || x[i].getAttribute('class') == 'changeImg')
    {
      x[i].onclick = function () {
      return changeImg(this.href)
      }
    }
  }
}

function changeImg(imgSrc) {
  document.getElementById('photo').src = imgSrc;
  return false;
}