在虚拟主机中，主域名是使用public_html目录/文件夹作为主域名的缺省目录，主域名网站的文件和程序都是放在public_html目录下，附加的域名(addon domains)使用public_html目录/文件夹下的子目录/子文件夹。有的人可能觉得public_html目录/文件夹下的会看起来比较乱，因此想把主域名也指向其中一个子目录/文件夹。这样就需要利用.htaccess的重写功能。
具体的写法如下：
# .htaccess main 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 main domain.
RewriteCond %{HTTP_HOST} ^(www.)?yourmaindomain.com$
# Change ’subfolder’ to be the folder you will use for your main 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 main domain.
RewriteRule ^(.*)$ /subfolder/$1
# Change yourdomain.com to be your main domain again.
# Change ’subfolder’ to be the folder you will use for your main domain
# followed by / then the main file for your site, index.php, index.html, etc.
RewriteCond %{HTTP_HOST} ^(www.)?yourmaindomain.com$
RewriteRule ^(/)?$ subfolder/index.php [L]
