Target Blank

<a href="#" target="_blank">Opens the linked document in a new window or tab</a>

<a href="#" target="_self"> Opens the linked document in the same frame as it was clicked (this is default)</a>

<a href="#" target="_parent">Opens the linked document in the parent frame</a>

<a href="#" target="_top">Opens the linked document in the full body of the window</a>

link_to "External link", "http://www.rubyonrails.org/", target: "_blank", rel: "nofollow"
# => <a href="http://www.rubyonrails.org/" target="_blank" rel="nofollow">External link</a>