Search Engines Optimization Tweak to htaccess file

Problem:

It is an important SEO issue because the SEs can view the www and non-www as 2 SEPARATE sites with identical content... and with the big deal the SEs are stressing right now w/duplicate content, no one wants their site to be penalized.

The results from testing should be the SAME destination URL in the address bar - no matter what someone types in. These instructions use the www as the destination - which is fine (the destination can be either the www or non-www)

Solution:

It involves creating a .htaccess file, or editing one that already exists in
the hosting account's files. The file should be in the highest level,
publicly accessible folder (usually called www/, htdocs/, or public_html/).
If the file already exists on the server in one of those directories,
download it onto your computer using an FTP program. If there isn't a file
there, you'll need to create one.
*
* *To create an .htaccess file:*-Open up Notepad
-Copy and paste the following into the file:

Options +FollowSymLinks
RewriteEngine On
RewriteBase /

RewriteCond %{HTTP_HOST} .
RewriteCond %{HTTP_HOST} !^www.domain-name.com [NC]
RewriteRule (.*) http://www.domain-name.com/$1 [R=301,L]

-*Replace "domain-name"* with the name of the domain. Replace "com" with the
appropriate extension (like "net") if necessary.
-Do File > Save As. In "File Name:", type "*.htaccess*", then choose "*Save
as Type: All Files*". Click Save.

--------------------
*To edit an existing .htaccess file (make sure that you make a backup of the
file before doing this):*-Open up Notepad
-Do File > Open and browse to the location of the .htaccess file you
downloaded onto your computer. In "*Files of Type:*" select "*All Files*",
and the .htaccess file should become visible in the file list.
-Check for the following, but do not replace or add this code if it's
already in the file. *If it's not there, add it.*

Options +FollowSymLinks
RewriteEngine On
RewriteBase /

-*Add the following:*

RewriteCond %{HTTP_HOST} .
RewriteCond %{HTTP_HOST} !^www.domain-name.com [NC]
RewriteRule (.*) http://www.domain-name.com/$1 [R=301,L]

-*Replace "domain-name"* with the name of the domain. Replace "com" with the
appropriate extension (like "net") if necessary
-Save the file.

----------------------

*After you're done*, put the file on the server using your FTP program. Make
sure that you put it in the highest level, publicly accessible folder
(usually called www/, htdocs/, or public_html/). After that, *check the
website* to make sure that everything is functioning properly.

*If you receive an error* like the one below, then something is wrong with
the .htaccess file, and you'll need to check it over to make sure that you
followed the steps above properly.

*500 Internal Server Error

The server encountered an unexpected condition which prevented it from
fulfilling the request.

*If you continue receiving the error after you've corrected the file (or if
you didn't have to), remove the .htaccess file from the server and/or revert
back to the backup file that you made (To revert, put the backup on the
server. Make sure that it's named ".htaccess").