jQuery scrollTop function
<p>I have one page where the next page is fired when the user reaches the bottom of the page:</p>

<pre><code>$(window).scroll(function(){
    if  ($(window).scrollTop() == $(document).height() - $(window).height()){
        next_funtion();
    }
});
</code></pre>

<p>However, I want next page to be fired when the user reaches 50% of the page height <em>or</em> 200 px from the top.</p>
