<img id="img" clicked="0" url="example.com" src="image.jpg" />

<script>
$(function(){
$("#img").click(function(){
var clicked = $(this).attr("clicked");
if(clicked == "0"){
$(this).attr("clicked", "1");
}else{
var url = $(this).attr("url");
location.href =url;
});
});
</script>