In reality, the only teaching aid which we can depend upon having in every classroom is the humble OverHead Projector, or OHP.
Problem: it is not possible with current browsers to sufficiently customise their printed output for OHP use. What we need is a software utility which can accept as input an HTML document, and generate as output a PostScript(tm) document which can be printed onto OHP transparencies and immediately used in a classroom situation.
We have built a (humble) prototype of such a utility.