Please can you help me to fix this :

Wait! We're detecting that you're not redirecting the non-www version of your website to the www version (or vice versa). By not doing so, you're creating essentially two versions of your website that can confuse the search engines when it comes time to rank your site.
Effects on trafficmaller infractions of duplicate content, like the www redirect (the one we're looking for here) can have a moderate impact on traffic. You may see after doing the proper 301 redirect from www to non-www (or vice versa) will result in moderately better rankings. Actual duplicate content, where you post the exact content on two different websites for instance, have a much higher impact. It is highly likely only one of those sites will rank with the content, and a small chance that both will not rank at all. Avoid duplicate content!
Doom Reviewed by Doom on . IPB help Duplicate Content (www redirect) Please can you help me to fix this : Rating: 5