function switchPic(obj) {
  var mp = document.getElementById('mainpic');
  mp.src = obj.childNodes[1].src;
  mp.parentNode.href = mp.src.replace(/235px/, 'max');
  return false;   
}

function switchPic2(pic) {
  var mp = document.getElementById('mainpic');
  mp.src = pic.src;
}