My approach would be to stick only the original version as the user entered it in a flat file, and stick the HTML-encodified version in the Application object.

Also, of course, in the Application_OnLoad event, I would read the file, HTML-encode it, and stick the result in the Application object.

On the other hand, if I had any suspicion that I would get a call that "I accidentally changed the text and I want to put it back to what it was", I would use a wiki-style data record (so that changes were kept in perpetuity.)