Remove website field from comment forms
If you wish to allow anonymous comments but remove the Homepage field, you can do so in either a custom module or theme function that implements hook_form_FORM_alter().  

Via a theme function (source, mengi on drupal.org):

function THEME_form_comment_form_alter(&amp;$form) {
  $form['author']['homepage']['#access'] = FALSE;
}


Or via a custom module:

function MYMODULE_form_comment_form_alter(&amp;$form) {
  $form['author']['homepage']['#access'] = FALSE;
}


Note: Anonymous comments may be reasonable if you use other anti-spam measures such as honeypot fields and javascript-filled anti-spam fields.