Message when using Sessions

Hey there when using sessions i have this message on the page::

Warning: Unknown: Your script possibly relies on a session side-effect which existed until PHP 4.2.3. Please be advised that the session extension does not consider global variables as a source of data, unless register_globals is enabled. You can disable this functionality and this warning by setting session.bug_compat_42 or session.bug_compat_warn to off, respectively in Unknown on line 0

Any one know of what it is?

Thanks so much!

You are putting an unset variable into session (most likely). [url=,mod=14&sourceid=chrome&ie=UTF-8&q=Your+script+possibly+relies+on+a+session+side-effect+which+existed+until+PHP+4.2.3.+Please+be+advised+that+the+session+extension+does+not+consider+global+variables+as+a+source+of+data%2C+unless+register_globals+is+enabled.+You+can+disable+this+functionality+and+this+warning+by+setting+session.bug_compat_42+or+session.bug_compat_warn+to+off%2C+respective]Other possibilities

Yah i am not sure why that showed up that time has not showed up again and i am allready in the process of a reformed script.