Many years ago Windows systems were more popular. Microsoft created CHM then. It was compressed archive/file including HTML files (with CSS, Java Script, etc.) with additional TOC, indexes and similar things. I have used it for various purposes and even today it's possible to open and read many of these files. Example for it can be "The HTML Reference Library 4.0" (my conversion of original release prepared by Stephen Le Hunte).

Historia znana od lat - jedni piszą oprogramowanie robiąc z tego swoje główne źródło utrzymania, inni robią z tego tzw. bazar lub wręcz religię... jedni wymagają (stałych lub jednorazowych) opłat, a inni rozdają to co napisali dosłownie za darmo... jedni wszystko patentują, inni się tym dzielą....

http://www.w3.org/community/webed/wiki/HTML/Specifications shows, that current version of HTML is 4.01 and version 5 is in draft only...but in the same time everybody is proving compliance with it. Big fun...that we're all using beta version of something and we're happy from it :)