Htaccess lines to permanently redirect secondary domains to a primary domain. For example: www.example.com/foo will redirect to example.nl/foo. And a lot of other examples.

.htaccess

# Only necessary for website not implemented with FifthGear
RewriteEngine On 

# Rewrite www.example.nl and example.com to example.nl
RewriteCond %{HTTP_HOST} www.example.nl [NC,OR]
RewriteCond %{HTTP_HOST} example.com [NC]
RewriteRule ^(.*)$ http://example.nl/$1 [R=301,L]

# Rewrite example.nl to www.example.nl
RewriteCond %{HTTP_HOST} ^example.nl [NC]
RewriteRule ^(.*)$ http://www.example.nl/$1 [R=301,L]

# Enforce HTTPS
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://example.nl/$1 [R=301,L]

# Exclude url from redirecting to HTTPS
RewriteCond %{HTTPS} off # Default operator is AND, so don't add [OR]
RewriteCond %{HTTP_HOST} !no-https.example.nl [NC]
RewriteRule ^(.*)$ https://example.nl/$1 [R=301,L]

# Make a file available for domain validation.
RewriteRule ^file-name.txt$ - [NC,L]

# Block all traffic to a domain
ErrorDocument 404 "This text will show up in the browser."
RewriteCond %{HTTP_HOST} example.com [NC]
RewriteRule ^(.*)$ - [R=404,L]

# Use Basic Auth to simply secure a page
<Files "secured-page">
	AuthName "This is a secured page"
	AuthUserFile /home/accountSystemName/app/website/.htpasswd # Search for a htpasswd generator for more information.
	AuthGroupFile /dev/null
	AuthType Basic
 	require valid-user
</Files>