I can't remember rewrite rules:
RewriteEngine On
RewriteCond %{HTTP_HOST} !^www\.your-domain\.com [NC]
RewriteRule (.*) http://www.your-domain.com/$1 [L]
RewriteCond %{HTTP_HOST} !^www\.other-domain\.com [NC]
RewriteRule (.*) http://www.other-domain.com/$1 [L]
RewriteEngine On
RewriteCond %{HTTP_HOST} ^(www\.)?addon-domain\.com [NC]
RewriteRule (.*) http://www.main-domain.com/$1 [L]
RewriteRule ^pet-care/?$ pet_care_info_01_02_2008.php [NC,L]