BlockLoadScripts

# .htaccess to block load-scripts.php and load-styles.php if user is not logged in.
#
# For styles, it redirects to the login.css, which includes *most* of the styles needed for the login screen. 
# For scripts, it simply denies access with a 403 Forbidden.  
#
# This workaround may have trouble if you have customized the login screen.  Add this code to the top 
# of your .htaccess file.
#

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteCond %{REQUEST_URI} load-styles\.php*
    RewriteCond %{HTTP_COOKIE} !^.*wordpress_logged_in.*$ [NC]
    RewriteRule (.*) /wp-admin/css/login.css [R=302,L]

    RewriteCond %{REQUEST_URI} load-scripts\.php*
    RewriteCond %{HTTP_COOKIE} !^.*wordpress_logged_in.*$ [NC]
    RewriteRule (.*) / [F]
</ifModule>