>Not being able to resize browser frames is a known issue for FireFox and Mozilla. As I use Mozilla I'm hoping that it is added in future versions.

Put your mouse cursor slightly above the thin black line separating the top and bottom frames.

Press and hold the right mouse button.

Drag the mouse down.

The cursor should then turn into a resize arrow.

Keeping the right mouse button held, you can click and hold the left mouse button to resize.