<HTML>
<HEAD>
    <script language=javascript>
function Test()
    {
       __doPostBack(Button1,"HELLO");
     }
    </script>
</HEAD>
<body MS_POSITIONING="GridLayout">
<form name="Form1" method="post" action="WebForm1.aspx" id="Form1">
    <input name="TextBox1" type="text" id="TextBox1"/>
                      <input type="submit" name="Button1" value="Button" id="Button1" onclick="return Test();" />
                  </form>
</body>
</HTML>