If you have several domain names parked/pointed at your site it is a good idea to create permanent 301 redirect for them so for the search engines not to treat them as duplicate content.
Here is a sample .htaccess that will do that:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^parkeddomain.com$ [OR]
RewriteCond %{HTTP_HOST} ^parkeddomain-2.com$
RewriteRule ^(.*)$ http://www.maindomain.com/$1 [R=301]
And even more generic solution would be:
RewriteEngine on
RewriteCond %{HTTP_HOST} !^www.maindomain.com$
RewriteRule ^(.*)$ http://www.maindomain.com/$1 [R=301]