Comment 1 for bug 719033

I had the same thing happen to me. Basically, I was downloading a series of images, one image at a time. The bottom tabs which report the progress and completion of file downloads are apparently a fixed size and there is no ability to scroll these from side to side. Hence, the window keeps getting expanded.

To clear this, grab the title bar with the mouse and move the window to the left until the right edge of the window appears. Then click on the bottom right tab {Clear} to clear completed download notifications.

dufeu