I got the link from
http://www.tech-recipes.com/rx/853/f...tronic_books_/
they further explain the meaning of the code there.
It's basically like searching for pictures or mp3 files. A code that reduces .html pages as search results.
whatever is posted on the internet I can not be held liable for it. The use of this code is not illegal neither, it just is a form of a search filter.
You can find legal pdf's as well! My first results where company pdf files that did not benefit me a lot.