Uppercase or lowercase?
In HTML it doesn’t really matter. You could have the elements in all caps (<HTML>), lowercase (<html>), or even in mixed-case (<hTmL>). The choice is a matter of personal preference, although future versions of HTML (the XML-compatiable XHTML) require elements to all be in lowercase. By using lowercase now, it could save a lot of work down the road.
Unlike HTML, though, CSS and JavaScript are case sensitive, so anExample and anexample are two different descriptors.