It is confusing for beginners in XML that the attributes of an element are not in a namespace if they don't have a proper namespace prefix. There is no default namespace for attributes. It is almost a rule that attributes are not in a namespace.
Processing Instructions are special tags with instructions to software making us of the XML document. It sounds important and makes PIs extremely confusing for novices. The truth is that PIs are seldom used with a few common exceptions
When I find something interesting about XML, easy to quote, I add it to this small collection of quotations about XML. Mail me If you know of a good piece that is missing jesper@tverskov.dk.
The standalone pseudo-attribute in the XML declaration is a mystery for many XML beginners. Most often it is irrelevant but it is tempting to add it or delete it or to change its value from "yes" to "no" to "yes" as long as you don't know what it is all about.
Updated 2008-11-09