For normal web page when a page becomes too long then we use same page hyperlink. That is if we are at the bottom of the page and want to move at the top then we click a link and that moves us at the top instantly. This is done in normal website by this way
<div id="atop">.....</div> lots of information..... ... ... <a href="#atop">Top Page</a>
So when user will click Top Page he will move to at the top. But If you want to implement the same thing in facebook app, then it will not work. There is different way to implement the same functionality.
<a name="ftop"></a> lots of information..... ... ... <a href="#ftop">Top Page</a>
Look at the code we used <a> tag and name attribute within the <a> tag. This is the only difference for facebook application. Checkout http://www.facebook.com/pages/Thinkdiffnet/314110374728?v=app_7146470109 and move at down and click Top Page. You’ll see that page is moving slowly to the top.