Position fixed when scrolled passed certain amount of pixels

Question

I\'m looking for a way to position the #header element of my page as \"Fixed\" only after having scrolled downward for about 170 pixels.

Above the header is a banner, so

Answer 1

I think this should work: http://jsfiddle.net/Skooljester/K2mFT/. However, you'll need to define a width on your header or else it'll shrink when it becomes fixed.