Leslie Lamport wrote an article on "How to Write a Proof" back in 1993. In it, he described the L^ATEX style pf.sty for writing structured proofs. This style makes it much harder to prove things that are not true. The pf2html project adds functionality to L^ATEX2HTML such that L^ATEX documents written with pf.sty can be viewed in a web browser up to the desired level of detail for each branch of a structured proof.