Only the data needs to be updated and not the whole JSP page

I NEED HELP IN FOLLOWINGS :
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1. the page needs to update the data in real time and the update time should be flexible ( I will be able to select the amount of seconds from the web page, some kind of field or drop down list)

2. only the data needs to be updated real time and not the whole page

3. if there is a scroll down bar and the data is updating, the position of the scroll down should be remembered.

do you know ajax or you ZERO on it ?

Have min idea of javascript..

Did you saw the examples of ajax here
ajax/my-first-ajax-application-t597.html
ajax/ajax-source-code-to-suggest-application-with-jsp-server-side-t599.html