Performing redirection fom non www to www or essential is a essential for SEO of a particular site because most of the search engines treat both www and non-www version differently and hence regard a single page as duplicate of other.
Search engines than put penalty on duplicate content in spite of the fact that your article is original and genuine.
This can easily be avoided by using .htaccess file in the root of your Website.
NOTE: This method is applicable only to those servers which allow mod rewrite in Apache(Linux) or IIS(Windows). Please confirm with your host.
Add following lines to redirect all www request to non-www version of your domain
RewriteCond %{HTTP_HOST} ^www.example.com$ [NC]
RewriteRule ^(.*)$ http://example.com/$1 [R=301,L]
Add following lines to redirect all www request to non-www version of your domain
RewriteCond %{HTTP_HOST} ^example.com [nc]
RewriteRule (.*) http://www.example.com/$1 [R=301,L]
In above two modification we use 301 redirect which means that a given page is permanently moved from this location thus telling search engines not to take this page as duplicate copy of other.