Server-side comments prevent server code (including server controls) from executing.
<%-- commented out code or content --%>
ASP+ server-side comment blocks have the same uses as traditional language-specific comment blocks, including documentation and testing.
Within <script runat="server"> </script>
and <% %>
blocks, you can use native language comment syntax.
You cannot use server-side comment blocks within <% %>
blocks. A compilation error will result.
The opening and closing comment tags may appear on the same line of code, or can be separated by one or many commented-out lines.
Server-side comment blocks can be nested.
ASP+ Page Syntax