I have the following snippet in my functions.php to add login warning text under the username & password fields.
I get the warning banner text as expected, however there is an issue that results in the banner text also apprearing at the top of the login page. You can see the issue at http://new.cubecolour.com/wp-admin
This code has worked perfectly on all WP versions I have used it on prior to 3.2 beta 1 – I am using it without issue on several sites running 3.12.
// Place Warning Banner On Page
$cc_sitename = get_bloginfo('name');
$cc_siteurl = get_bloginfo('url');
echo '<p style="color: #909090;"<strong>Authorised access only</strong><br /><br />
Disconnect immediately if you are not an authorised user.</p>
<p style="color: #909090; text-align: right;"><a href="' . $cc_siteurl . '/">' . $cc_sitename . '</a>
<br /><br /><br /></p>';