Simple ! Set
Display="None" in the Validator tag as:
<p> Name :
<asp:TextBox ID="txtName" runat="server" />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ErrorMessage="you still no add the name !" Display="None" ControlToValidate="txtName"></asp:RequiredFieldValidator>
</p>
and Validation summary as:
<asp:ValidationSummary ID="ValidationSummary1" runat="server" HeaderText="the all error that meet to is : "></asp:ValidationSummary>