Comments are notations that you can make on your web pages within an
ASP script block that will not be interpreted or output on the
displayed web page(s).   For all intents and purposes, they
are hidden from your site visitors since they cannot view the ASP
source code for your web pages.  This allows you to make comments
inside your code that will help explain exactly what your code is doing.

Active Server Pages use the quote character (‘) to define comments. This
comment is a “line comment”, meaning that it will comment out everything
following it up until the end of the line. There is no multiline comment in ASP.  
In order to comment multiple lines, each line must be preceded by a quote
 (‘).

<%
' example comment - show the current date
Response.Write "Now()"
%>

Besides not having any support for multi-line comments, your ASP comments
will not work if you place them within a string. This is because the interpreter
will think that your apostrophe is a part of the string and not a comment. Below
is an example of this happening.  Again, the following is an example of what not to do!

<%

Dim newVar1, newVar2

newVar = “Hello. ‘I am not commented out”

%>