13.4. Style Options
Mozilla has a special styling system for <trees>. <listbox>, on the other hand, is mundane.
The listbox system has no Mozilla extensions unique to the CSS2 style system. It does, however, have an extensive set of style rules and id'ed tags to which styles can be applied. These rules appear in xul.css in toolkit.jar and in listbox.css in the global skin (e.g., in classic.jar). All those files are in the chrome.
XUL has some unique and specific style functionality. This functionality is used for trees, which are styled differently than all other tags. All the body of a given tree, specified as content of the <treechildren> tag, can be styled directly from a treechildren selector. A style extension ...