A little seen effect in modern web design is the parallax effect or parallax scrolling. Parallax involves layered images that move at different speeds from background to foreground, creating depth and if designed cleverly enough, the illusion of 3D space. The effect can be achieved with plain old CSS and HTML, as well as with jquery powered javascript application jparallax.
One of the most well known individual examples of CSS within the web design community of CSS-based parallax is on Clearleft’s landing page for their Silver Back App. The vines at the top of the page are set as parallax layers.
The images look great as a set of layered static images but there is no mouse interactivity, and the effect can only been seen “in action” while the browser window is being re-sized. Designer Paul Annett says using parallax in such a subtle way where not everybody sees it is “like a hidden Easter egg for those who do.” You can view a full explanation of the css that Paul used for the effect on his article here.