Authorize.net payment gateway issue

on my wordpress theme, i have a membership module that offers different levels of subscriptions to my users. However, my payment gateway is authorize.net and whenever someone fills in the payment fields and clicks submit, it seems as though the submit is not sending. Here is of the code i pulled from the gateway.authorizenetaim.php plugin file:

 $form .= '<form method="post" action="#" class="membership_payment_form authorizenet single">';
    $form .= '<div class="message error hidden"></div>';
    $form .= '<input type="hidden" name="subscription_id" value="'.$subscription->id.'" />';
    $form .= '<input type="hidden" name="user_id" value="'.$user_id.'" />';
    $form .= '<table class="membership_cart_billing">';
    $form .= '<thead><tr><th colspan="2">'. __('Enter Your Credit Card Information:', 'membership'). '</th></tr><开发者_如何学运维;/thead>';
    $form .= '<tbody><tr><td align="right">'. __('Credit Card Number:', 'mp'). '*</td>';
    $form .= '<td><input name="card_num" onkeyup="cc_card_pick(\'#cardimage\', \'#card_num\');"';
    $form .= 'id="card_num" class="credit_card_number input_field noautocomplete" type="text" size="22" maxlength="22" />';
    $form .= '<div class="hide_after_success nocard cardimage"  id="cardimage" ';
    $form .= 'style="background: url(' . $M_membership_url . 'membershipincludes/images/card_array.png) no-repeat;"></div></td></tr>';

The form action of # will cause this error. It should be the URL of the page that will handle the submission.