new Ajax.Updater(container, url[, options])

• container (String | Element) – The DOM element whose contents to update as a result of the Ajax request. Can be a DOM node or a string that identifies a node's ID.
• url (String) – The URL to fetch. When the same-origin policy is in effect (as it is in most cases), url must be a relative URL or an absolute URL that starts with a slash (i.e., it must not begin with http).
• options (Object) – Configuration for the request. See the Ajax for more information.

Creates a new Ajax.Updater.