Hi,
here is some basic idea, this may help you,
1) once you create any html file store it on server folder.
2) you can use System.IO to read file content and display it in any WYSIWYG(What you see is what you get).
3) you can use iFrame or WYSIWYG control to view as html page.
Or
you can purchase this paid
Teleric Editor or
FCK Editor
Thanks
-Amit.