Not able to validate when i set causevalidation =false

Hi,
If I set causevalidation of my button control to false, my validation control does not work..(Requiredfield validator for textbox does not work)

If i set it to true (which is by default), postback does not happen ( Hence, nothing happens even after clicking on button)
what is the solution? what may be the reason ?
 
 
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="sweethome.aspx.vb" Inherits="sweethome" EnableSessionState="True" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
                                             &nbs ...