Break out of parent div's

When i have a div with position: absolute, and in it is another div with position: absolute the inner div will position in the frame given through the outer (wrapper) div. Now i want to create a class (css) called error_message that positions itself exactly in the center middle of the site, indifferent from where the it is called, so i need it to break out of every div wrapped around the error_message div.. how do i do this?