p. With HTML, developers knew where they stood: design, content, and styling were all in one place. However, the new (and superior) trend is towards keeping various parts of data separate: XML stores content, CSS stores styling, and XHTML stores layout.
p. Using the new system, with content and layout clearly split, it is suddenly much easier to manipulate content without affecting layout. This is where XSLT comes in: it provides a way to process and output the data stored in an XML document based upon your processing instructions.
