Hi Lawson,

I guess that happens only in IE6/7. That "tooltip" is not really a "tooltip", but the alt attribute, which should be rendered for any IMG element. That is displayed as a tooltip due to a bug (or a special feature) in IE.
Application may get around that by removing the value for corresponding property. The default is "[Default]" and actual text is coming from resources depending on culture and type of editor. For WebDatePicker it should be "Drop Down Calendar" and for all other editors it should be "Custom Action" (assumes that if application implemented custom action, then it will adjust value of alt/AltText and/or title/ToolTip properties of button).

Example to remove:

<ig:WebDatePicker ID="WebDatePicker1" runat="server">
   <Buttons>
     <CustomButton AltText="" />
  </Buttons>
</ig:WebDatePicker>