I've noticed that on some sites, StackOverflow included, that if I start writing a post (Title, description etc), then leave the page - I might come back and click on the 'Ask Question' link a day later and the details are prefilled exactly from where I was the day before.

I was wondering how this is best achieved when developing a site using ASP.NET MVC? I was thinking that storing it in Session would expire after x minutes and it'd be too much to try to store in a cookie?