Display default text in textbox when a MaskedEditExtender is attached to it

Question

I am using MaskedEditExtender and MaskedEditValidator to validate time entered by the user in a textbox it works fine on my computer but when I deployed it on the server the default text I want to display in the text box is not getting displayed in it intead the text box gets displayed with empty text. My code is shown below :

<asp:TextBox ID="txtToTime" runat="server" Width="60" Text="23:59:59"></asp:TextBox>                        
<asp:MaskedEditExtender  ID="mexToTime" runat="server" TargetControlID="txtToTime" Mask="99:99:99" MaskType="Time" />
<asp:MaskedEditValidator ID="MaskedEditValidatorToTime" runat="server" 
                         ControlExtender="mexToTime" ControlToValidate="txtToTime" 
                         InvalidValueBlurredMessage="*" MaximumValueBlurredMessage="*" 
                         MinimumValueBlurredText="*" Display="Dynamic" ErrorMessage="*"  />

i have tried to use javascript to display text in the textbox when page gets loaded but even it don't work for me. Any suggetions how to display text "23:59:59" in the textbox when page gets loaded.