closebutton Obsolete since Gecko 1.9.2
Type: boolean
If this attribute is set to true, the tabs row will have a "new tab" button and "close" button on the ends. This feature is used by the tabbrowser to provide the facilities for adding and closing tabs. You can set an image to the "new tab" and "close" buttons by applying them to the tabs-newbutton and tabs-closebutton classes respectively.