Quick CSS inspector

Click the extension icon to switch on the inspector's mode, and click any target inside the current page. Then the page will be covered by a light mask, the box model of the selected item will be shown with a small window displayed beside to tell the calculated css values. The window is draggable. Click anywhere on the mask except the window will close up the current displaying. Refresh the page, or Click the extension icon again to switch off the inspector's mode, the page will be recovered to the original status.