How do I control formatting and appearance

How do I control formatting and appearance?

Answer:

In HTML, default styling was built into the browsers because the tagset of HTML was
predefined and hardwired into browsers. In XML, where you can define your own tagset,
browsers cannot possibly be expected to guess or know in advance what names you are
going to use and what they will mean, so you need a stylesheet if you want to display
formatted text.
Browsers which read XML will accept and use a CSS stylesheet at a minimum, but you
can also use the more powerful XSLT stylesheet language to transform your XML into
HTML—which browsers, of course, already know how to display (and that HTML can
still use a CSS stylesheet). This way you get all the document management benefits of
using XML, but you don't have to worry about your readers needing XML smarts in their
browsers.