How do I refresh a div using jquery and ajax?

How do I refresh a div using jquery and ajax?

Hello
I need to know how to refresh only one div using jQuery and AJAX.

Basically, here what I am doing. When a user log on the site using jQuery and AJAX I need to update the header by displaying "Welcome back, BLAH" also i can to change the buttons in the header to add "sign out and my account buttons!"

it is very smiler to this web site when you log in the buttons in the header change!

Note that i have the buttons and the name in a div and they all change via PHP and cookies but i need to to change with out refreshing the whole page.

Thanks