Please, I appologise, but what exactly is menaing "this" in front of inner...in this code:
<h1 onclick="this.innerHTML='Ooops!'">Click on this text!</h1>
It basically means "change the text of this element to 'Ooops!' when it's clicked on".
As said, though, it's lousy code, so don't use it, but read the reference supplied instead.