option 2
Let's assume that you directly want to render XML contents in a browser. This content may be text-centric XML that you created yourself, contents using a document standard, contents that are pulled out of a database or that are obtained through a web service, e.g. a simple RSS news feed. In most cases, you would use XSLT for styling, i.e. translate XML to HTML or another markup language. However, using CSS is easier and can do a perfect job for some text-centric contents.
A valid XML document is defined in the XML specification as a well-formed XML document which also conforms to the rules of a Document Type Definition (DTD). ... In other words a well formed XML document does not need a DTD, but it mustconform to the XML syntax rules.