asp buttonimage alternate text not visible

I've a problem with asp:image and asp:imagebutton alternate text: it's not visible when I move the mouse over the image. I declared the object in that way:

<asp:ImageButton ID="Bu开发者_开发百科ttonStatus" 
ImageUrl='<%# IIF(Eval("Active")=1,"../images/folders/actived.png","../images/folders/deactivate.png")%>' CommandName="ChangeStatus" CommandArgument='<%# Eval("id_repository") %>' OnCommand="FolderCommand" 
Enabled = '<% #iif(mySecurity.Admin=1, "True", "False") %>' Width="24px" AlternateText="Change the status"
runat="server" />

and for asp:image

<asp:HyperLink runat="server" ID="url_groups" NavigateUrl="~/action/Group_manager.aspx?action=2">                                                 
    <asp:Image id="img_groups" runat="server" ImageUrl="~/Images/folders/group_config.png" AlternateText="Group manager"
    EnableViewState="false" ImageAlign="Middle" Width="32px" CssClass="navigation" />
</asp:HyperLink>  

Could you help me? I tried to search on web but I wasn't able to find any post or suggestion to fix that problem

thanks, Andrea

It's browser dependent whether the alt text gets shown when you mouse over an image. If you set the ToolTip parameter on a .NET Image or ImageButton it will render a title attribute which shows across pretty much every browser.

Here's an example from a site I'm currently working on:

<asp:HyperLink ID="ReplyLink" runat="server" NavigateUrl='<%# Eval("SrcAddr", "~/msp/send.aspx?to={0}") %>'>
    <asp:Image ID="ReplyIcon" runat="server" ImageUrl="~/images/email_go.png" AlternateText="Reply" ToolTip="Reply" />
</asp:HyperLink>

I think you're mixing up the alt attribute with the title attribute. Alt is shown when the user doesn't accept images and for screen readers whereas the title attribute is shown as tool tip when you hover the image.