To include comments in an HTML document that will be ignored by the HTML user agent, surround them with <!-- and -->. After the comment delimiter, all text up to the next occurrence of --> is ignored. Hence comments cannot be nested. White space is allowed between the closing -- and >, but not between the opening <! and --. Comments can be used anywhere within an HTML document and are generally used as markers to improve the readability of complex HTML documents.

For example:

<TITLE>The HTML Reference Library</TITLE>
<!-- First created by Stephen Le Hunte, March 1995 -->

NOTE: Some browsers incorrectly consider a > sign to terminate a comment.