In the mailer_form.html page I have a field 'Email'. The form submitter has to put in his email. The form submit action is -
<form name="form1" action="<%db_cgi_url%>/mailer.pl" method="POST" onsubmit="return checkFields(this);">

What I want is when the form is submitted, it should check that the Email of the submitter is in the database (ie is only the people who are in the database can send messages). If the email ID is not there then mailer_error.html page should show up else the mailer_success.html page should show up.