Wordpress Admin Colors

[brookrobinson]

Hello people!

Wondering if someone could help! Im trying to follow the tutorial from WP..here..
codex.wordpress.org/Creating_Admin_Themes#Creating_an_Admin_Theme_Plug in

Heres what i have upto now!
Plugin file:
<?php

/*
Plugin Name: Customcms
Plugin URI: http://www.example.co.uk
Description: This plugin will change your wordpress admin colour scheme. There are no options for the plugin, just install and activate! To change the colour scheme, simply download the style sheet and edit the colours.
Author: ME
Version: 1.0
Author URI: http://www.example.co.uk
*/

function my_admin_head() {
echo '<link rel="stylesheet" type="text/css" href="' .plugins_url('wp-admin.css', __FILE__). '">';
}

add_action('admin_head', 'my_admin_head');

?>

Heres the css (just as explained in the tut)
@charset "utf-8";
/* CSS Document */

#wphead {
border-bottom: MidnightBlue 1px solid;
background-color: #E4F0FE!important;
background: -moz-linear-gradient(bottom,#E4F0FE,#B0C4DE);
background: -webkit-gradient(linear,left bottom,left top,from(#E4F0FE),to(#B0C4DE));
}

THE BIG PROBLEM!
I cant get it to work!...can anyone point me in the right direction, or explain what im doing wrong?...the plugin is showing up and allowing me to activate it, but no changes to the admin??

Hope someone can help, thanks in advance.