Image Button alternate text (tooltip) is not working in ie 8 asp.net

To solve the Image Button alternate text is not working in ie 8 asp.net problem
follow the below code

.aspx

asp:Image ID="imgItinerary"   ImageUrl="~/images/search_thumb.jpg" runat="server"

.aspx.cs


Problem created code:
                i missed out tooltip property

                imgItinerary.AlternateText = "Image";

Solution for the above problem:
             
                imgItinerary.AlternateText = "Image";
                imgItinerary.ToolTip = "Image";