QUOTE(Peter1968 @ Feb 26 2007, 01:28 PM)
One way I can think of off the top of my head would be to embed the markup you want to illustrate inside an iframe and have the server deliver it as text/plain.
Except that a certain browser-like OS component is likely to interpret it as text/html anyway.
Another option is to post a sample document, and let them View Source if they want to copy the source.
Another option is to create a simple script to do the conversion for you.