Create an aspx button :
asp:button text="Click Me" runat="server"

In the server side add the button client side functions.

btnOpen.Attributes.Add("onClick", "return false;");
btnOpen.Attributes.Add("onMouseOver", "mousemoveover();");

Javascript function to move the button

function mousemoveover()
{
var btn = document.getElementById("btnOpen");
var sHeight = screen.height - 400;
var sWidth = screen.width - 100;
btn.style.marginLeft = Math.floor(Math.random()*sWidth) + 'px';
btn.style.marginTop = Math.floor(Math.random()*sHeight) + 'px';
}