Mouse click the middle of the screen

[InterestedNewbie]

This is probably a simple question, but I can't find it in the documentation. I need to create a script that will click exactly in the middle of the screen. regardless of screen resolution, monitor type or (Active) window. 
How do I do that?

[Gintaras]

lef 0.5 0.5

[InterestedNewbie]

Thank you Gintaras, that works!