You may have noticed in your Google webmaster tools that there are duplicate home pages – one is yoursite.com/home and the other is simply yoursite.com
To avoid the duplicate pages, a simple redirect via the url-rewrite method is all that’s needed to avoid this duplicate content.
By default, Magento’s main page is called ‘home’, so Google treats these as 2 separate pages.
go to catalog/url-rewrite management in your admin control panel and ‘add Url rewrite – select type of ‘custom’ and fill in the fields as shown below:
You’ll notice that the target path is “../” – this is so it’ll go to the default index page of your Magento Home directory. You could also specify the exact url if you prefer (ie http://yoursite.com) or a different path if your store is located in a subfolder.