I am doing it wrong in JavaScript

Yeah, JS is a scripting language and not a programming language, whatever. Anyway, I've got a page where the script does the following a couple of times:

var i = document.createElement('div');
i.innerHTML = 'some text';
i.class = 'some CSS class';
document.getElementById('element already in the page').appendChild(i);

I'm not >>1-7
JavaScript is a really frustrating language to work with. First, things seem to work (or more often, not work) by art of magic. Second, you get almost no input in what went wrong. Sometimes your browser goes DO NOT WANT and at best you'll have the JavaScript console. Third, there are n different versions of JavaScript where n is the number of browsers supposedly supporting JavaScript ever released; all of which are different in very subtle ways that make everything fail for one reason or another; and if you want cross-browser compatibility, you have to code everything a number of times, and your script ends up being made of hack and dirty.