Travis Smith

WordPress’s themes are absolutly amazing, except you are not able to theme the login pages very well. Smithers Login is a light weight plugin that will allow you full theme control over the WordPress Multisite login pages. This plugin allows for different custom login screens on a single WordPress 3.0 Multisite with Domain Mapping. This Network Activated plugin enables you to specify a stylesheet to be used with every multisite login page allowing for custom login images and messages.
Some Features:
<ul>
<li>Specify CSS style sheet for login pages.</li>
<li>Change the URL and TITLE of the header link.</li>
<li>Add a custom image to the login page with PSD file.</li>
<li>Add specific messages to the different login pages (Login, Registration, Forgot Password)</li>
<li>Change various error messages on login and registration pages.</li>
<li>Enhances and extends DBD Login Style.</li>
</ul>

Smithers Login

Add style to your WordPress multisite login pages! This plugin enables you to specify a CSS to be used on the login page with a custom image/messages.

Maxaud

This plugin allows you to define different CSS rules that get loaded into the page’s for specific devices.
Includes checks for 18 different tablet options and 13 different phone options.
This can be useful if you need to target specific phones or tablets to make CSS changes or show certain advertisements for certain devices.
For more options or if you feel like donating, check out the <a href="http://codecanyon.net/item/mobile-css-pro/3182318/" title="Mobile CSS Pro" rel="nofollow ugc">PRO version of Mobile CSS</a> that is available for purchase.

Mobile CSS

Allows you to define different CSS styles that get loaded for specific mobile devices.

Smithers Login vs Mobile CSS