Validation error in Contact a Board Administrator

1 error validation in .../memberlist.php?mode=contactadmin

Bad value for attribute action on element form: Must be non-empty.

<form method="post" action="" id="post">

For example:

http://validator.w3.org/check?uri=http%3A%2F%2Fgugolplex.tk%2Fmemberlist.php%3Fmode%3Dcontactadmin&charset=%28detect+automatically%29&doctype=Inline&group=0&user-agent=W3C_Validator%2F1.3+http%3A%2F%2Fvalidator.w3.org%2Fservices