CSS Sans: a font made with CSS only
CSS is the language used for styling web pages, from layout to typesetting. It used to be very limited, but progressed quite quickly to allow web designers to create more complex designs.
One Japanese web developer, Yusuke Sugomori, took CSS much further with his experiments. He designed a full font using HTML and CSS only. While the font might not be very usable in web design as is, it is still an awesome way to test the limits of CSS capabilities.
The greatest part of this project might very well be the attention to details and the great presentation work. The best part is probably the hover effect on each CSS declaration that shows you in blue what the declaration is doing.