XML Binding Language (XBL, sometimes also called Extensible Bindings Language) is a language for describing bindings that can be attached to elements in other documents. The element that the binding is attached to, called the bound element, acquires the new behavior specified by the binding. Bindings can contain event handlers that are registered on the bound element, an implementation of new methods and properties that become accessible from the bound element, and anonymous content that is inserted underneath the bound element. scrollbar { -moz-binding:url('somefile.xml#binding1'); }