Be aware of rel="nofollow" for links – Google Search Engine Optimisation Starter Guide User Manual
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Google's Search Engine Optimisation Starter Guide, Version 1.1, 13 Nov 2008, latest
directories or subdirectories in your robots.txt file and guess the URL of the content that you
don't want seen. Encrypting the content or password-protecting it with .htaccess are more
secure alternatives.
Avoid:
•
allowing search result-like pages to be crawled (users dislike leaving one search
result page and landing on another search result page that doesn't add significant
value for them)
•
allowing a large number of auto-generated pages with the same or only slightly
different content to be crawled: "Should these 100,000 near-duplicate pages really
be in a search engine's index?"
•
allowing URLs created as a result of proxy services to be crawled
Be aware of rel="nofollow" for links
Setting the value of the "rel" attribute of a link to "nofollow" will tell Google that certain links on your site
shouldn't be followed or that your page's reputation shouldn't be passed to the pages linked to.
Nofollowing a link is adding rel="nofollow" inside the link's anchor tag.
If you link to a site that you don't trust and to which you don't want to pass your site's reputation,
use nofollow
When would this be useful? If your site has a blog with public commenting turned on, links within those
comments could pass your reputation to pages that you may not be comfortable vouching for. Blog
comment areas on pages are highly susceptible to comment spam. Nofollowing these user-added links
ensures that you're not giving your page's hard-earned reputation to a spammy site. Many blogging
software packages automatically nofollow user comments, but those that don't can most probably be
edited manually to do this. This advice is also relevant for other areas of your site that may involve user-
generated content, such as guest books, forums, shout-boards, referrer listings, etc. If you're willing to
vouch for links added by third parties (e.g. if a commenter is trusted on your site), then there's no need
to use nofollow on links; however, linking to sites that Google considers spammy can affect the
reputation of your own site. The Webmaster Help Centre has more tips on
such as using CAPTCHAs and turning on comment moderation.