Used to define the anonymous content of a binding. The elements within the content tag become the anonymous content of the element bound to. The content is visible on screen as if it was present directly in the XUL file, however the elements cannot be seen via the normal DOM functions.
You can place the XBL inherits attribute on any element within the content. This is used to have attributes of the bound element be placed on the inner content. This attribute must be in the XBL namespace.
Type: element id, must be unique in the window
A unique identifier so that you can identify the content with. You can use this as a parameter to getElementById and other DOM functions and to reference the element in style sheets.