make sure all of the files are saved to your computer and then delete them all, they should no longer be in your website and be "unpublished"
--------------------------------------------
if you meen delete the website tottaly well thats simple.
if you use html just delete all of the files
if your using wizard...delete all of the pages
a simple way if your using a free acount is to just create another website because it automaticly overwrites the old one