what if i do not set error message in required field validator?

Question

If i do not set error message in required field validator, will it display msg pop up box or not? my code-

<asp:RequiredFieldValidator runat="server" SetFocusOnError="true" 
  ValidationGroup="Search" ID="RFV_ddlTimeSlot" Display="None" 
  ControlToValidate="ddlTimeSlot" InitialValue="--Select Time Slot--"
  ErrorMessage=""></asp:RequiredFieldValidator>

Answer 1

So it will still validate the control but will not show any message.

Answer 2

Whenver your control have invalid values and validation occurs your RequiredFieldValidator will show a *.

Answer 3

Yes it will still validate. Why not spend 5 mins trying it out?