Help with rotation

[Sample D Light]

I'm trying to make a ground plane rotated "80 degrees" as per others instructions so that I have a base for rendering shadows. I create a cube wich I then use the Initialize-Z size to make thin, and I make sure that the Gyo-widget has been perfectyly aligned, then rotate it 80 in the "X" which is the horizontal axis, but it won't rotate in only the X axis. It gets all skewed and crooked, I also noticed that if the rotation seems different if you move the tool preview plane around to get a better view an whats happening. Why is this?
If I am constraining the rotation to only the X axis then why is it rotating in other axis? I'll keep trying and hopefully can figure this out.

[Sample D Light]

Never Mind. I figured it out! I pressed the reset on the tool preview plane and now that its aligned I get perfect rotation. I just don't understand why moving the preview plane effects the objects rotation.

[aurick]

All deformations are relative to the orientation in the preview window, rather than on the canvas.

The easiest way to rotate a plane is to draw it on the canvas and then bring up the rotation gyro. Then go to Transform>Modifiers>Info and set the X to 80, Y znd Z to 0