when I click on any button on my page it start refresh whole page and reload it why ?
can any help in this............

Because buttons cause postback and a postback is essentially a page refresh.

@sodabread
thanks for such a quick reply.....
Is there any way stop that..........because when surf any web page and click on any button this should not happen there

Do you want only client scripts to execute upon button click?
In that case, I suggest using an ordinary input-html tag.

<input type="button" value="Button Text" id="yourButtonId" />

And attach a click event in client code.