Custom Admin CSS styles to style media uploader?

Its likely that you’re not enqueing your CSS file to be used in the admin area, however you did not say. Anyway, this is what you can do…

Place the following into your functions.php file:

add_action( 'admin_print_styles', 'my_admin_css' );
add_action( 'wp_enqueue_scripts', 'my_admin_css' );

function my_admin_css(){
   if( is_admin() ) {
    wp_enqueue_style(
        "media_upload", 
        get_bloginfo('template_directory')."/css/custom_admin.css", 
        false, 
        false, 
        "all"
    );
   }
}

Where ../css/custom_admin.css is an assumed directory and file in your theme folder.

You can learn more about the various methods to handle both scripts and CSS files for both the front end and admin starting with,

http://codex.wordpress.org/Function_Reference/wp_enqueue_style

…the rest of which can be found under the miscellaneous functions section here

http://codex.wordpress.org/Function_Reference#Miscellaneous_Functions

…and you shall see related functions at the bottom of each individual function page like that of the above wp_enqueue_style.

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