To help prevent vBulletin from generating duplicate content, it is suggested that you add a robots.txt file to your forum root. The below code prevents search engines from crawling unnecessary urls and indexing duplicate content, along with other miscellaneous urls you don’t want to clutter your search listings with.
User-agent: *
Disallow: /clientscript/
Disallow: /cpstyles/
Disallow: /customavatars/
Disallow: /customprofilepics/
Disallow: /signaturepics/
Disallow: /customgroupicons/
Disallow: /images/
Disallow: /includes/
Disallow: /install/
Disallow: /archive/
Disallow: /ajax.php
Disallow: /announcement.php
Disallow: /attachment.php
Disallow: /calendar.php
Disallow: /converse.php
Disallow: /cron.php
Disallow: /editpost.php
Disallow: /faq.php
Disallow: /global.php
Disallow: /group_inlinemod.php
Disallow: /groupsubscription.php
Disallow: /infraction.php
Disallow: /inlinemod.php
Disallow: /joinrequests.php
Disallow: /login.php
Disallow: /member_inlinemod.php
Disallow: /misc.php
Disallow: /moderation.php
Disallow: /moderator.php
Disallow: /newattachment.php
Disallow: /newreply.php
Disallow: /newthread.php
Disallow: /online.php
Disallow: /payment_gateway.php
Disallow: /payments.php
Disallow: /picture_inlinemod.php
Disallow: /posthistory.php
Disallow: /postings.php
Disallow: /printthread.php
Disallow: /private.php
Disallow: /profile.php
Disallow: /register.php
Disallow: /report.php
Disallow: /reputation.php
Disallow: /search.php
Disallow: /sendmessage.php
Disallow: /subscription.php
Disallow: /threadrate.php
Disallow: /usercp.php
Disallow: /usernote.php
if you already have a robots.txt file, simply edit it, and add the above lines to your code (check for duplicates). If you do not have a robots.txt file, create one and add the above code to it. Save and upload to your forum root directory.