Prototype

In the API docs on http://www.prototypejs.org, there are good explanations about the Event.element(e) method, but not much about the 'this' reference that refers to the element on which the event handler was originally set. This can be confusing for the beginner.

For Element#observe, here is the current code example:

$(element).observe('click', function(event){
  alert(Event.element(event).innerHTML);
 });
// -> HTMLElement (and will display an alert dialog containing
// element's innerHTML when element is clicked).

I don't know if this would be fine, but I suggest a new example as something like this to explain the purpose of 'this':

$(element).observe('click', function(event){
  // this -> a reference to the element on which the 'click' event handler was originally set
  // Event.element(event) -> gets the element where the event occured

  alert(Event.element(event).innerHTML);
 });
// -> HTMLElement (and will display an alert dialog containing
// element's innerHTML when element is clicked).

Or maybe a small explanation about event bubbling could be nice.

It's all up to you guys, this was just my suggestion.