Question:What are the parameters of open method of XMLHttpRequest object? 

The parameters of open method of XMLHttpRequest object are :
method: The HTTP method used to open the connection,such as -GET,POST,PUT,HEAD,or PROPFIND
URL: The requested URL
asyncFlag: A boolean value indicating whether the call is asynchronous.
userName: The user name
password: The password

Question:What are the functions of responseText and responseXML properties? 

ResponseText holds the response body as a string.Which function is read-only.
ResponseXML holds the response body as XML.This function is also read-only.

Question:What are the values of readyState property? 

0 uninitialized
1 loading
2 loaded
3 interactive
4 complete

Question:Why status property is used? 

The Status property indicates the combined values of the operation and error status code. The Status property for each Field can be used to determine why the Field was not added, modified, or deleted.

Question:What is onreadystatechange event? 

 The onreadystatechang is an property of XMLHttpRequest object.The onreadystatechange event is triggered every time the readyState changes. It stores a function (or the name of a function) to be called automatically each time the readyState property changes

Question:Which information is return by getResponseHeader method? 

The getResponseHeader method is used to get only data for a specific header, the “Last-Modified” header, like this:
XMLHttpRequestObject.getResponseHeader(“Last-Modified”)

Question:How can you get overcome caching with the Http framework? 

The Http framework supports forced caching in Firefox as well as forced non-caching in Internet Explorer. Internet Explorer caches the response from the server by default, so clicking the top Get Time button always gives us the same time. But the Http package can avoid caching (which it does by appending unique data to the end of an URL each time we call the URL). For example, when we click the second button from the top in the figure, the time is updated for each button click, even in Internet Explorer.