function setPostcard(val) {
	var imgSrc = this.getHref();
	var previewImage = document.getElementById('postcard_preview').getFirstChild();
	previewImage.setSrc(imgSrc);
	document.getElementById('selected_postcard').setValue(val);
	return false;
}
document.getElementById('postcard4').getFirstChild().addEventListener('click', setPostcard(4));
document.getElementById('postcard5').getFirstChild().addEventListener('click', setPostcard(5));
document.getElementById('postcard6').getFirstChild().addEventListener('click', setPostcard(6));