Guide reformats HTML code

We have created some nicely formated and very basic HTML pages that we want to incorporate as part of our customer FAQ. Nevertheless, when we try to copy/paste the code, initially it is correctly previewed, but when we click the update button, then it gets re-formated and all the magic goes away. We have already invested some time into this and would like to know if there is any chance of working around this very inconvenient product "feature".