RE: < a > tag vs ImageButton

Hi,
in the following code I have an <a> tag that works perfectly, and I'm trying to replicate the same functions to substitute it with an ImageButton. The ImageButton causes the postback, and instead I want only the clientClick (to call a modal popup in jQuery)
Here's the code:
<asp:Repeater ID="sortableRepeater" runat="server" > <ItemTemplate> <li id='<%#Eval("idphotoimage")%>'> <asp:Image ID="Image1" ImageUrl='<%#Eval("image")%>' runat="server" /> <asp:ImageButton ID="ImageButton1" ImageUrl="images/edit.gif" CausesValidation="false" onClientClick='return editfunction(<%#Eval("idphotoimage")%>);' runat="server" /> <!-- <a id="popoutUsers" href='editPhotoGalleryImage.aspx?id=<%#Eval("idphotoimage")%>' onclick='return editfunction(<%#Eval("idphotoimage")%>);' >edit&l ...