no invalid message show in dijit.form.ValidationTextBox

[gen2000]

hi,
I'm testing the dijit form validation widget, but there is no invalidMessage show.
Please help.

      <input type="text" name="userName" id="userName" size="20"
      dojoType="dijit.form.ValidationTextBox"
      required="true"
      propercase="true"
      promptMessage="enter first name"
      invalidMessage="first name is required."
      autocomplete="on"
      trim="true"
   
      />