var links = document.getElementsBySelector('#screenshots a');
var handler = function() {
	 document.getElementById('screenImage').src = this.href;
	 for (var i = 0, count = links.length, element; i < count; i++) {
		element = links[i];
		element.className = element == this ? 'active' : '';
	 }
	 return false;
};
for (var i = 0, count = links.length, element; i < count; i++) {
	element = links[i];
	element.onclick = handler;
}