htaccess code clarification

[fine0023]

I have the following code in my htaccess (but with my actual domain name of course), and I'm not sure if I understand exactly what it is all for....I was just wondering if someone could help explain precisely what this means.

#if the domain is not www.mydomain.com
RewriteCond %{HTTP_HOST} !^www\.mydomain\.com$ [NC]
#redirect to www.mydomain.com
RewriteRule ^(.*)$ http://www.mydomain.com/$1 [L,R=301]

#leave this rule in place, but after the one above to handle the home page
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /index\.html\ HTTP/
RewriteRule ^(.*)index\.html$ http://www.mydomain.com/$1 [R=301,L]

[handlegeek]

#if the domain is not www.mydomain.com
RewriteCond %{HTTP_HOST} !^www\.mydomain\.com$ [NC]
#redirect to www.mydomain.com
RewriteRule ^(.*)$ http://www.mydomain.com/$1 [L,R=301]

This is for redirecting from non-www domain to www domain
Example:

mydomain.com -> www.mydomain.com

NC => no case comparison
R=301 => 301 redirect
L => Last condition[/CODE]

#leave this rule in place, but after the one above to handle the home page
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /index\.html\ HTTP/
RewriteRule ^(.*)index\.html$ http://www.mydomain.com/$1 [R=301,L]

This is to extract directory path (uppercase letters - length between 3 to 9 characters) for the URLs ending with index.html and redirect to directory path.
For example:

www.mydomain.com/TEST/index.html -> www.mydomain.com/TEST/

%{THE_REQUEST} => Request URI (Ex:TEST/index.html)

For more details: http://www.ganeshbabujayaraman.com/a...and-drupal-cms

[fine0023]

I was wondering if it is necessary to keep all of this code in my htaccess....because I have www.mydomain.com set as my hard canonical name, which I think is supposed to redirect aliases such as mydomain.com automatically (without having to code anything in htacess). However, I don't think this has anything to do with redirecting index.html to the non-index.html url. Would it make sense to take out the first part:

#if the domain is not www.mydomain.com
RewriteCond %{HTTP_HOST} !^www\.mydomain\.com$ [NC]
#redirect to www.mydomain.com
RewriteRule ^(.*)$ http://www.mydomain.com/$1 [L,R=301]

and leave in the second part:

#leave this rule in place, but after the one above to handle the home page
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /index\.html\ HTTP/ 
RewriteRule ^(.*)index\.html$ http://www.mydomain.com/$1 [R=301,L]

?

[mike333]

Rewrite rules don't actually "hide" URLs, they just change them. In order to have a dynamic value be passed to the script it must be visible in the URL. You could, however, use a rewrite rule to add a static GET parameter to a URL that doesn't have one or to convert a visible part of the URL into a GET parameter.