We have similar login/register forms at Radbox (http://radbox.me ). Both register and login forms are default provided by web2py enclosed by div and styled using css on enclosing div.
e.g.
<div class="authform" style="display: none;">
{{=auth.login()}}
<p>{{=A('Forgot password?',
_href=URL(request.application,'account','user/retrieve_password'))}}</p>
</div>
form is styled with css on authform class.
