From this article you will know how to forbid search engine bots indexing and following certain links.

Solution

Tools:

• microformat rel="external nofollow", which is added to link body (for Google)
• embrace link with tag (for Yandex)

Modules for managing site links indexing:

• Links managing in taxonomy and menu
• Inserting rel="nofollow" white or black site list to external links
• Using of the standard feature of Filter module

Using of the standard feature of Filter module

Open the required input format (for example, /admin/settings/filters/1/configure)
Check "Protection against spam links"
Set "Sorting" for correct displaying of document body

Effect of this method applies to Filter module operational area. Especially these are fields where user can select input format…

Links managing in taxonomy and menu

Using nofollow module

White and black site lists to manage indexing

nofollowlist module allows creating white and black site lists. Links are indexed and NOT indexed respectivelly for sites from one of the list.