This page uses slants to make the triangle, and a single 211 bytes image file for the "raster bars". The image is a PNG-file with full alpha transparency, so IE can't show it correctly. Using both a solid background color and a semi-transparent background image on top of it gives the appearence of a fading bar. In Opera, you can turn images off to see just the colors move. You can use Opera's full screen projection mode to change the appearence of the page.