is there a way i can dynamically update my webpage without any user action whenever there is a change made in the daatabase.

eg gmail automatically updates your email whenever you get a new one....

Lets say i am viewing a page which shows all those who have signed up for a newsletter on my site. whenever there is a new sign up can he/she be dynamically added to the list i am currently seeing without me refreshing or performing any action that would trigger it?