How to mark something as viewed when a user clicks on a row.
Here is an example what I am trying to explain: http://www.dba.dk/dyr/hunde-og-tilbehoer/racehunde/race-labrador/ Try to click on a row and go back. You will see the row is marked with a check sign. So you know you have seen it.
How to create something like it?
You’re looking to save an AJAX history state. Two Amazing Rails and Javascript tutorials can be found here :
http://railscasts.com/episodes/246-ajax-history-state
http://railscasts.com/episodes/175-ajax-history-and-bookmarks
The first link will reference the second.
From Ryan Bate’s Website | Railscasts.com