Question

Just visit http://techcrunch.com/ and scroll down. How do they do it? How that top line appears with a new logo? Is there any jQuery trick? How to determine when person scrolled down certain amount of pixels and show to him new html?

Answer 1

They might just use jQuery-Waypoints which lets you trigger events if the user “passes” a certain HTML-Element.

Example ( taken from page ):

    $('.entry').waypoint(function() {
       alert('You have scrolled to an entry.');
    });