malimg

<img class="userimg" data-src="http://i.imgur.com/a8oCZdF.jpg" src="http://i.imgur.com/ad2hK61.gif"><br />
<script>
$(document).ready(function() {
	// http://api.jquery.com/jquery.ajaxtransport/
	$.ajaxTransport("image", function(s) {
		if (s.type === "GET" && s.async) {
			var image;
			return {
				send: function(_ , callback) {
					image = new Image();
					function done(status) {
						if (image) {
							var statusText = (status === 200) ? "success" : "error", tmp = image;
							image = image.onreadystatechange = image.onerror = image.onload = null;
							callback(status, statusText, {image: tmp});
						}
					}
					image.onreadystatechange = image.onload = function() {
						done(200);
					};
					image.onerror = function() {
						done(404);
					};
					image.src = s.url;
				},
				abort: function() {
					if (image) {
						image = image.onreadystatechange = image.onerror = image.onload = null;
					}
				}
			};
		}
	});
	$("img.userimg").each(function() {
		var current_image = $(this);
		if (current_image.data("src") != undefined) {
			$.ajax({
				username: "dummy",
				password: "dummy",
				url: current_image.data("src"),
				type: "GET",
				cache: true,
				dataType: "image",
				processData: "false",
			}).done(function() {
				current_image.attr("src", current_image.data("src"));
			}).fail(function() {
				current_image.attr("src", "http://i.imgur.com/mfxjbZM.png");
			});
		}
	});
});
</script>