When Web Inspector is set to open in a separate window, each new Web Inspector window is 22 points taller than the previous Web Inspector window (approximately the height of a window title bar). STR (tested with Safari 8.0 (10538.43.40), OS X 10.10 (14A283o)): 1. Open any page in two tabs in Safari. 2. On the first tab, open the Web Inspector. 3. If the Web Inspector is docked to the browser window, click the toolbar button to detach it into a separate window. 4. On the second tab, open the Web Inspector. Expected: The two Web Inspector windows should be the same dimensions, and the position of the second window should be offset slightly from the position of the first, as with other windows in the OS. Actual: The two Web Inspector windows overlap exactly, and the second Web Inspector window is 22 points taller than the first. Notes: This issue has been present for several versions of OS X, and is also present in Chrome's developer tools.
<rdar://problem/17663254>
Wow, how have we never noticed this before? Good find.
This got fixed at some point before the final release of Safari 8.