<!-- and ending tag --> placed at
the beginning and end of EVERY line to be treated as a
comment. Comments do not nest, and the double-dash sequence
"--"
may not appear inside a comment except as part of the closing
-->
tag.
Do not try to use this to "comment out" HTML that would otherwise be shown to the user, since some browsers (notably Mosaic) will still pay attention to tags inside the comment and close it prematurely.
(obtained from the WWW faq list)