A ".htaccess" is a file that can change settings on the
servers and allow you to do many different things such as alter
.shtml extensions and create custom 404 and 505 error pages. .htaccess
files are used most on Unix or Linux servers, or any version of
the Apache web server. You do however have to have permission from
your host to use a .htaccess file. Along with the above things a
.htaccess file can also password protect folders and redirect users
automatically.