We've gotten a lot of the syntax and rules of creating XML documents at the element and character data level down now. It's time to move on to the next level: actually giving your document structure.
The W3C has a lot of rules about how to structure your document in a way to make it well-formed, and I'll take a look at those rules here. In this chapter, I'm going to talk only about standalone documents; in Chapter 3, we'll see that we have to adjust these points somewhat for documents that have a DTD.
If you have doubts whether your XML document is well-formed, use an online XML validator, such as the excellent one hosted by the Brown University Scholarly Technology Group at ...