If I come back to a web site after having filled in a form previously, the browser remembers my username (for example). I'm not talking about cookies remembering user names and passwords, but the way a browser will suggest a value for a previously submitted field.

What controls this behaviour?

My issue at the moment is that I have login forms on several small apps all running under the one domain. (eg www.example.com/app1/login/ and www.example.com/app2/login/). If I use my user name for app1, then go over to app2 where I use a different username, it only ever auto suggests my app1 user name.

How can I change this behaviour? Do browsers use the fields ID to help remember this stuff? If I change the ID of the fields in the login form, will they auto suggest the correct values in future?