Answer: Depends on what quadrant it starts in/on.
Explanation:
Quadrant 1 is the top-right corner.
Quadrant 2 is the top-left corner.
Quadrant 3 is the bottom-left corner.
Quadrant 4 is the bottom-right corner.
Depending on what quadrant you started on will determine what quadrant you're on after rotating 90 degrees counter-clockwise.