Here is a snippet for you to add to your WordPress site to customise the CSS of the WordPress Admin Area. This is useful if you want to hide elements, change their colours etc - basically you can add any styles you want. Add this to your site's functions.php file:-
Replace 'your-theme-name' with your actual theme name and now simply create a 'styles' directory in your theme if you haven't already got one and then add a CSS file called admin.css. All you now have to do is add your CSS styles in the admin.css file as normal - So Easy!
What if I'm using WordPress Multisite?
We've got you covered. Just change 'site url' on line 06 to 'network_home_url'.