How to prevent a user from having multiple instances of the Same Web application

Question

I\'m wondering if it is possible to determine if a user already has a web browser open to the web application I\'m working on. It seems that they can open several instances

Answer 1

We have implemented a solution to this problem on the slicethepie.com. Users (or "scouts") are only allowed to have one browser window open at a time to ensure they listen to the music they are being paid to review.

When a scout requests the first track to review in their scouting session we set a new Guid on their account and return this "key" along with the details of the track they're being given to review. It happens that the recipient of this key is a flash movie, but it doesn't have to be. The key is re-submitted along with the scout's review, and we check to see if it matches the saved key. If it doesn't they've started a new scouting session in a new window.

I'm not implying this method is foolproof, but it could be adapted to your needs quite easily.