XUL is an XML application that is similar to HTML. It's no surprise that familiar attributes from HTML also apply to XUL.
id. XML supports the concept of tag identity, simply called id. HTML's id attribute is named id. XUL's id attribute is also named id. That is straightforward.
style. Inline styles can be specified for XUL as for HTML.
class. As with HTML, CSS syntax makes it particularly easy to apply style rules to elements of a particular class, or to all elements of the same class.
onevent handlers. XUL tags support most DOM inline event handlers like onclick. They are numerous and covered in Chapter 6, Events.
XUL also has its own set of generally useful attributes, like flex, debug, height, and width