This happens many times to me: I search on Google for a problem I’m having with my computer, click on a search result, reach the site (most of the time, it’s a forum), and boom! I have to register in order to view the solution on the page. Or worse, on some occasions, they want me to pay them to view the page.
http://www.makeuseof.com/tag/3-ways-to-access-must-sign-up-to-view-sites/