Search engines see and as two separate sites. Therefore, if each are indexed, you run the risk of having your site penalized as having duplicate content.

Additionally, and would be seen as being separate pages, although they are the same content, and could divide your incoming links.

There is a way to control this, so that the search engines only index what you want.

Here is some code you can place in your .htaccess file to accomplish both of the scenarios above:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} ^domain\.com [NC]
RewriteRule ^(.*)$$1 [R=301,L]
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9} /(([^/]+/)*)index.html HTTP/
RewriteRule index.html$$1 [R=301,L]

This code will make redirect to
It will also redirect and to