Hide Caption Titlebar causes the window content to be displaced when mousing over certain areas and controls. These areas includes mousing over the left window edge as well as leaving any control on the topmost area (buttons, location bar, search bar or tab). When this happens the window content is shifted right and up, approx 10 and 5 pixels, respectively, and a border to be displayed around the full inside of the window area, overwriting existing contents, the border being thicker to the left and bottom, and thinnest to the top. This border disappears after about half a second and the content is shifted back to its original position. This bug has followed me since FF4 and only disabling the addon makes the glitch go away.