.htaccess

RewriteEngine On
RewriteBase /

ErrorDocument 404 /404.html
RewriteRule ^(_js)($|/) - [L]

Options -Indexes

# If (SITE A DOMAIN or SITE A SUBDOMAIN) 
RewriteCond %{HTTP_HOST} ^www\.maratropa\.com$ [NC,OR]
RewriteCond %{HTTP_HOST} ^maratropa\.com$ [NC]
# make sure we haven't already rewritten this URI
RewriteCond %{REQUEST_URI} !/maratropa/index.php
# don't rewrite if the resource already exists
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
# rewrite
RewriteRule ^(.*)$ /index.php?user=$1 [L,QSA]

# IF !(SITE A DOMAIN or SITE A SUBDOMAIN) 
RewriteCond %{HTTP_HOST} !^www\.maratropa\.com$ [NC,OR]
RewriteCond %{HTTP_HOST} !^maratropa\.com$ [NC]
# make sure we haven't already rewritten this URI
RewriteCond %{REQUEST_URI} !/index.php
# don't rewrite if the resource already exists
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
# rewrite
RewriteRule ^(.*)$ /maratropa/index.php?user=$1 [L,QSA]