!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
// Your page here
It assigns the compressed body of the outer assign macro to the variable "out", and the finally writes the value of "out" with all newlines stripped.
The entire page is now a singe line of HTML - a developer's nightmare, but a nice a bandwidth saver.
Combined with Sitemesh, another one of my favorite tools, this is easily and transparently applied to all your pages.