If you are using an earlier version of vBulletin:
You should add the Certify Code to these three vBulletin templates: footer, SHOWTHREAD_SHOWPOST, and Memberinfo. Once the code has been added to all 3 templates, you will be able to get your site’s metrics Certified.
If you are using vBulletin 4+:
You should add the Certify Code to these 4 vBulletin templates: footer, whoposted.php, printthread.php, and Memberinfo. Also, if your site has an archive section, you should also add the code to your site’s index.php file.