Take a look at dropbox's website here:
Have you noticed how the footer with "Learn more" remains fixed at the bottom regardless of window resizing until you click or scroll down?
position: absolute;
bottom: 50px;
left: 0;
width: 100%;
text-align: center;
cursor: pointer;
The CSS above pertains to the footer, but it's not responsible for the effect.
I'm struggling to figure out how this effect is achieved. Any ideas?