Choose only any one [ www or non-www ]

You would have seen some websites/web pages with www while some without it. For most of the readers, it doesn't make any difference, actually they may not even notice it most of the times. But for search engines, it matters a lot. Search engines like Google, consider them as separate web pages or web sites. That means, when someone links to your website, as he may/may not use the www prefix to the link, so according to that the PR juice will be distributed between the www and non-www versions of your same original blog/website, moreover as search engines consider them as separate web pages, so your blog may get penalized for duplicate content issues :) that's true...

So to avoid these issues, go to Google and tell it's bot to consider both the www and non-www versions are same for your blog:
Follow these steps:

1. If you already have your account in "Google Webmaster Tools", and have submitted your blog's sitemap, then proceed or else read and add the sitemap to Google first.
2. Now once your account is active, then go to Settings Page, and in the "Preferred Domain" section, select any one radio button, as you like [either www or non-www]

For more information, regarding this, you can read the direct instructions from Google - Here

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