.htaccess not regarded on Debian by default
I set up a Debian server and was befuddled for some time about why my .htaccess in the default server was not being obeyed. This was a Virtualmin install, but It turns out to have nothing to do with Virtualmin and everything to do with Debian's more-secure-by-default configuration.
To enable .htaccess processing in the default server, use your favorite text editor on /etc/apache2/sites-available/default (on some other distributions this may be /etc/apache2/sites-available/000-default ) and right at the top you will see:
<VirtualHost *:80>
ServerAdmin webmaster@localhost
DocumentRoot /var/www
<Directory />
Options FollowSymLinks
AllowOverride None
</Directory>
<Directory /var/www/>
Options Indexes FollowSymLinks MultiViews
AllowOverride None
Order allow,deny
allow from all
</Directory>
Change the two instances of AllowOverride None
to AllowOverride All
...and all should be well.
With Webmin you can also go to Servers: Apache Webserver: Global Configuration: Edit Config Files; and select the sites-available/default for editing right in your browser.