Original Referrer & Anonymous Leads

Jamie's answer is not always correct.  Depending on the way the lead navigates to/through your site, the Original Referrer may mark the page they are viewing when they become known by filling out a form. In this case, it's the junction point between Anonymous and Known.  It is not the first time they hit your site.

Another point I'm obliged to make is that if your site is not running over , you cannot reliably obtain referrer information. This is because any links to your site from sites (such as secure search engines or any other SSL site) will only pass their referrer to you if you too are running .  Otherwise, your browser will see no referrer and analytics will mistake the traffic for Direct.  I can't emphasize this point enough because people think Marketo is sometimes "losing" the referrer, when it's the browser itself that doesn't have this information due to longstanding browser security rules.