function externalLinks() {
	if (!document.getElementsByTagName) return;
	var anchors = document.getElementsByTagName("a");
	for (var i=0; i<anchors.length; i++) {
		var anchor = anchors[i];
		if (anchor.getAttribute("href") && anchor.getAttribute("rel") == "external")
		anchor.target = "_blank";
	}
}

function changeSource(num) {
	document.getElementById('mainImage').src = 'gallery/'+num+'.jpg';
	document.getElementById('mainImage').alt = String(num);
	document.getElementById('galleryCaption').innerHTML = captions[num-1];
}

function prevPhoto() {
	if (document.getElementById('mainImage').alt != '1') {
		var currentIndex = document.getElementById('mainImage').alt;
		var previousIndex = Number(currentIndex) - 1;
		changeSource(previousIndex);
	}
}

function nextPhoto() {
	if (document.getElementById('mainImage').alt != '21') {
		var currentIndex = document.getElementById('mainImage').alt;
		var nextIndex = Number(currentIndex) + 1;
		changeSource(nextIndex);
	}
}

function galleryThumbs() {
	for (i=1; i<=21; i++) {
		document.write("<a href=\"javascript:changeSource("+i+");\"><img src=\"gallery/"+i+"t.jpg\" alt=\"\" width=\"60\" height=\"45\"/></a> ");
	}
}