Unknown exit links present in stats
Unknown exit links appear in the stats. An exit link is in the Top exit links report, and has been used by a visitor to leave a site, but it is not an existing link published on a site.
Clickstream data is drawn from click-paths traveled by your visitors through a browser. An exit link is not necessarily an existing link from your site, but is a part of the clickstream of one of your visitors.
Opentracker does not track bookmarks, meaning that the person did not use a bookmark to exit. So where does the link exist?
An important question to ask is how many people have followed the link. If it is just one, you have an isolated event. If there are numerous visitors leaving, then perhaps a pop-up or pop-under? Pop-ups are indeed a possibility, perhaps a spyware program released a pop-up while a person was on your site. Some spyware insert html with exit links into the source of a page. so it would appear as a 'genuine' exit link.
The explanation that we have found in the past is that there are numerous ways that people navigate away from a site through a browser. We are referring to navigational devices that people install on their computer which suggest links and content.
For example, a toolbar which suggests alternative sites that are content-related. In one case, a webmaster wrote to ask how somebody had followed a (non-existent) link from his site to a pornography site. His site had the word 'adult' in the title, and we found that the visitor had followed a link suggested by a toolbar. It turned out that the toolbar suggested the adult site because it appeared to be related content, due to the word 'adult'.
The point is that exit links which appear in your stats are not necessarily physical links located on your site.