The Extensible Binding Language, a Mozilla
project. XBL is a markup language
for describing bindings
that can be attached to elements in other documents. XBL can be used to bind elements within the host document to CSS
XBL is somewhat feature-compatible with XSLT, however XBL is dynamic, allows apparent access to the original source document (that is to say, XBL adorns the document with the new code rather than integrating it), modifies the source document rather than replicating it, is logically faster in the way it binds to CSS, and can dynamically bind to alternate stylesheets.