Mark - probably the best way to get started is to follow one of these
tutorials. They are easy to follow but will walk you through getting a basic site set up (with menus and dynamic content). In 30 minutes or so you will be familiar with the tags and snippets you will use most often.
As Susan said above, MODx will work with whatever you give it. You have complete control of everything that is output, so if you want HTML5, xml, martian, whatever... you can have it. It really is as simple as marking up a static HTML page, dropping your markup in a template, then replacing your content with the right
tags.
