What sort of a link is this?

Found it on a website that shows up in search of inbound links

[DelliTranswait]

What sort of a link is this?

 
 <input type='hidden' id='ref' name='ref' value='mydomain.com' />

Why would the owner of a website have a link to my website ('mydomain.com') in this form?

[mack]

Did you see that after clicking a link from your site to his.. looks as if it might be some sort of click tracking script?

Mack.

[DelliTranswait]

I found site via Google (searching for websites linked to mine). I only visited it to verify that there was a link to my site.

[lexipixel]

What was the action= value in the <form>?

[jtara]

Well, as an aside, I see a potential problem here: this is not a LINK to your site! It is a REFERENCE to your site. A hidden one at that.

Does Google not know the difference between a link and the mention of your domain name without an actual HTML link? (e.g. an A tag)

Wonder what they do with a reference to a domain in a comment?

Back to your question: was there, in fact, a link to your site on the page? If so, I'd guess that Google sets the "referrer" header to YOUR site rather than google.com when a user clicks on a SERP link from a link: search. Not sure why they would do that, if that's the case. Anyway, the site might want to keep track of the referrer for the session, and this is a way to do so without using a cookie.