Dear Stano,
I am using "password protected pages" plugin for members pages as "Log in". It works great! But I want to make a java script  "Log out" link (or button). When a member clicks on it, the cookies will be delete and the user goes out from his page for re entering his password.
Is it possible?

"I appreciate for your help"

Perfectly possible. Since jquery is already included I recommend using a jquery plugin like jquery-cookie

Could you please explain more about the usage of jquery-cookie?

How can i combine it with the "password protected plugin?"
Thank you

Include it and use

$.removeCookie('the_cookie');

Like it says in the documentation. Maybe give add some parameters to the call to make it work properly.