Working with pop up.
I need to create a pop up window if user has not selected certain things. And telling that , through a message on this window.Means I need a pop up window, flashing a message " Please enter the details" and
destroying it on pressing ok.It should appear at the center of screen.And it should not have option of minimising and maximising window( pop up window should have a ok button and a cross to close it)..........
This is new to me, please guide me step by step.