jquery: $(window).scrollTop() but no $(window).scrollBottom()
<p>I want to place an element to the bottom of the page whenever the user scrolls the page. It's like "fixed position" but I can't use "position: fixed" css as many of my clients' browser can't support that.</p>

<p>I noticed jquery can get current viewport's top position, but how can I get the bottom of the scroll viewport?</p>

<p>So I am asking how to know: $(window).scrollBottom() </p>
