If you have a dual monitor setup you might decide to undock some of your Netbeans windows, for example for running XDebug sessions or PHPUnit testing.
However you will find that by default, Netbeans sets the transparency of these windows to unreadable levels when they are not active.
This really defeats the object and is quite irritating.
I spent a long time under the false impression that this was some errant compiz setting and trying to figure it out that way.
Turns out that this is a Netbeans “feature” and you can disable it with a single untick of a box.
untick the “Transparent floating windows” box
Enjoy lots of usable desk space in Netbeans!