event
Optional event object. Required for any auto mouse positioning so you need to capture the mouse event and pass it in some way to this request.

querytString
The querystring for the request. This is typically set to provide context to the page that is being called to return specific data.

postData
Any explicit POST data you want to send to the server. Must be UrlEncoded. The post data might be ammended depending on your postbackMode setting.

errorHandler
A client side function that is called with a CallbackExcpetion object if an error occurs.