This isn't really a JS question, but more of a UI/Human Factors type question.

I'm looking for the topic of Dirty Page Notification.

Use Case:

User has some modifiable data (widgets/ forms, et c).
User changes some data, and must be notified in some way that the page is "dirty".

In GUI apps in the OS (say MS Word, or Eclipse), we have an asterisk by the file that is not saved, or will say "Unsaved Changes" in the window title bar.

So what are some best-practices for dirty page notification on the web?

And examples?