DIVs that are aware of their position, or the window's scroll position?
<p>In jQuery, how do you make it so a DIV will stay put until the user scrolling down would make it no longer visible (at which point it sets its own CSS position to "fixed")? It's a trick I see a lot, just not sure how it's done.</p>

<p>Example: <a href="http://www.yelp.com/search?find_desc=sushi&amp;ns=1&amp;find_loc=San+Francisco%2C+CA" rel="nofollow">http://www.yelp.com/search?find_desc=sushi&amp;ns=1&amp;find_loc=San+Francisco%2C+CA</a></p>
