Referral.
We add utm_source=namepros.com to each external link to make it easy to see how many visitors came from NamePros.
You can also add a unique query string (e.g., ?t=npsig) to the link in your signature to track exactly how many visitors came from your signature only, in case there are links elsewhere on NamePros (e.g., in posts) that also link to your site.
We hope this helps.