Hmm, this is kinda the wrong forum, you should have asked in the DOM forum instead. However, I trust a mod will be here soon and correct that for you. So, I'll get to explaining it instead:
Now, I'm not going to delve any deeper into this, as there are too many methods, properties and pecularities to mention in a post, but instead refer you to <http://www.w3.org/DOM/DOMTR
> where you can find all the DOM specifications. This isn't always the most easy-to-read set of documents, however, so I will refer you to <http://www.w3schools.com/dhtml/dhtml_dom.asp
> for tutorials, <http://www.quirksmode.org/
> for browser support tables, and us for help.