function imgSwap() {
	var thumbs = document.getElementById('product-thumbs').getElementsByTagName('img');
	for (var i = 0, j = thumbs.length; i < j; i++) {
		thumbs[i].onclick = swapThis;
	}
}

function swapThis() {
	var mi = document.getElementById('master-image');
	mi.src = this.src.replace('/thumb', '/thumb');
	mi.parentNode.href = this.src.replace('/thumb', '');
}

if (window.addEventListener) window.addEventListener('load', imgSwap, false);
else if (window.attachEvent) window.attachEvent('onload', imgSwap);