The XML FAQ

Yes, very easily, but at the moment there is still a need for more tutorials, simpler tools, and more examples of XML documents. ‘Well-formed’ XML documents may look similar to HTML except for some small but very important points of syntax.

The big practical difference is that XML has to stick to the rules. HTML browsers let you serve them even fatally broken or ridiculously corrupt HTML because they don't do a formal parse but elide all the broken bits instead. With XML your files have to be completely correct or they simply won't work at all. One outstanding problem is that some browsers claiming XML conformance are also broken, and some browsers' support for CSS styling is dubious at the best. Try yours on the test files at http://xml.silmaril.ie/test.xml and http://xml.silmaril.ie/hotels.xml.