"Glassy" windows?

[Macamba]

Hi,

All of a sudden I can see through the top window. I see the window below it. Hence the glassy window.

Does anyone know how this is caused, and more important, what I can do to change it?

TIA,
Macamba

[gettinoriginal]

Alt + scroll wheel (up or down) changes the opacity of windows via compiz. If you want to change it permanently, System > Preferences > CCSM > Accessibility, untick or change settings in opacity, brightness and saturation. :p