Ok, I'm using the sample file editHTML.aspx to edit a template that I created. Basically, it's a 3x3 table where some cells have the attribute UNSELECTABLE="ON" and some do not. This works well.
I am not able to block the user from editing the Body tag. I put UNSELECTABLE="ON" on the body tag, but it still lets me edit. Is that a bug or a limitation? I also tried creating a 100% height and width DIV on the page and set UNSELECTABLE="ON". This block editing most of the page, but you can still type under the DIV.
I am also working on what rights are necessary for saving the HTML file, but I have not worked that out.