.htaccess How to make a subfolder the main folder for your primary domain

gistfile1.txt

#From: http://support.lunarpages.com/knowledge_bases/article/549

# .htaccess primary domain to subfolder redirect 
# Copy and paste the following code into the .htaccess file 
# in the public_html folder of your hosting account 
# make the changes to the file according to the instructions.

# Do not change this line.
RewriteEngine on
# Change yourdomain.com to be your primary domain.
RewriteCond %{HTTP_HOST} ^(www.)?yourprimarydomain.com$
# Change 'subfolder' to be the folder you will use for your primary domain.
RewriteCond %{REQUEST_URI} !^/subfolder/
# Don't change this line.
RewriteCond %{REQUEST_FILENAME} !-f 
RewriteCond %{REQUEST_FILENAME} !-d
# Change 'subfolder' to be the folder you will use for your primary domain.
RewriteRule ^(.*)$ /subfolder/$1
# Change yourdomain.com to be your primary domain again. 
# Change 'subfolder' to be the folder you will use for your primary domain 
# followed by / then the main file for your site, index.php, index.html, etc.
RewriteCond %{HTTP_HOST} ^(www.)?yourmaindomain.com$ 
RewriteRule ^(/)?$ subfolder/index.php [L]