Duplicate Content

Be smart about the site structure: to keep the engines from crawling and indexing HTTPS pages, structure the website so that HTTPs are only accessible through a form submission (log-in, sign-up, or payment pages). The common mistake is making these pages available via a standard link (happens when you are either ignorant or not aware that the secure version of the site is being crawled and indexed).
Use Robots.txt file to control which pages will be crawled and indexed

Use .htaccess file. Here's how to do this:

Create a file names robots_ssl.txt in your root.

Add the following code to your .htaccessRewriteCond %{SERVER_PORT} 443 [NC]RewriteRule ^robots.txt$ robots_ssl.txt

Remove yourdomain.com:443 from the webmaster tools if the pages have already been crawled

For dynamic pages like php, try< ?phpif ($_SERVER["SERVER_PORT"] == 443){echo "< meta name=" robots " content=" noindex,nofollow " > ";}?>

Dramatic solution (may not always be possible): 301 redirect the HTTPS pages to the HTTP pages - with hopes that the link juice will transfer over.

Duplicate content generally refers to substantive blocks of content within or across domains that either completely match other content or are appreciably similar.