Steps to reproduce: 1. Open a Firefox 9.0.1 (all addons are disabled) 2. Maximize the window through maximize button 3. Type http://www.wikipedia.org/ in the address bar and press Enter //Monitor is in portrait view and my resolution is 1080x1920 and my start menu's auto hide is enabled Actual result: When browser's window is maximized top border appears (see attached screenshot.png). Also a element is hovered when you place mouse above it (see attached screenshot.png) and it's not when you place mouse at the bottom of it. Expected result: There should no be top border when you maximize browser's window and elements should be hovered or clickable only when mouse is placed exactly on them.

I saw the same issue. And it seems all links on the web page are displayed with an small offset.

Forgot to mention I saw it on both release 19 and beta 20.

This bug only happens when Windows 7 Aero is disabled automatically. I see this issue on Dell Latitude E6510 with NVIDIA NVS 3100M. I don't see this issue on Dell Optiplex 960 with ATI Radeon HD 3400, on which Windows 7 Aero is enabled.

I cannot reproduce the issues with mouse events so duping to a bug about the titlebar gap. Please file a new bug if the mouse events are incorrect in the portrait orientation.