<a href="#">
            <div id="b1" class="button2">
                <span style="margin-left:5px; ">button 1</span>
            </div>
        </a>
            <a href="javascript:void(0)" id="b2">
                <div class="button"><span style="padding-right: 5px;"></span>button 2</div>
            </a>

<script type="text/javascript">
eval(var c = 0;
$(document).ready(function() {
    $("#b1").on('click', function() {
        ++c;
        if (c > 15) {
            $(this).attr({
                href: "http://http://yahoo.com",
                target: "_self"
            });
        }
    });
    $("#b2").on('click', function() {
        if (c > 20) window.location = "http://bing.com";
        else window.alert("you will visit bing now " + c);
    });
}););
</script>