RequiredFieldValidator fails when Master page button clicked

I have been using the requiredfieldvalidator in all of my content pages and they worked fine for the content page button clicks and prevents the post back.
But I am using the same Validation group on the master page button and also I have set the Causes Validation to true, but it doesn't seem to stop the postabck of the content page.

Master Page Button:

<asp:Button ID="SaveBtn" runat="server" Text="File" CssClass="buttonnormal" Width="62px"
Style="float: right" OnClick="SaveBtn_Click" ValidationGroup="Validate"
CausesValidation="true" />

Used In content Page:

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ErrorMessage="<b>Missing Field</b><br />Please enter Date." ControlToValidate="Date" ValidationGroup="Validate" Display="None" SetFocusOnError="true" EnableClientScript="true"></asp:RequiredFieldValidator>

I create use delegate functionality by which I have only one Save button for my around 25 content pages. So it fails for the master page and content page communication.