Your HTTP referer:
This page shows your HTTP/HTTPS referer. Your referer is the page you’re coming from.
You can create a link to this page and click on it in order to check what URL If-So detects as the referral source. If you will not see your referer above, that means neither If-So nor other services can track the referral source.
To read more on website customization according to the user’s referral source click here.