customized login block
You could alter the form on the theme layer to wrap the form in a div...

/**
 * Implements hook_form_alter().
*/
function YOURTHEME_form_alter(&amp;$form, &amp;$form_state, $form_id) {

    //dsm($form_id);

    if ($form_id == 'YOURFORMID') {
        // add prefix and suffix to form
        $form['#prefix'] = '&lt;div class="form-class"&gt;';
        $form['#suffix'] = '&lt;/div&gt;';
    }
}