How to Log Off on close of a window?

Hello experts,

How do we call the log off if the user closes the window without clicking on log off link?

We have customized the portal header. Can some one help me on the code snipet which needs to be called on the window close event.

Thanks for the help.

Regards,

Nirmal Sivakumar G

Edited by: Nirmal Sivakumar G on Aug 24, 2009 7:30 PM