What is the correct way to reference an image in ASP.NET for live deployment on IIS?

The following works in dev and production:

<asp:ImageButton ID="ibnEdit" runat="server" OnClick="ibnEdit_Click" ImageUrl="~/App_Themes/Default/images/one.png" Visible="false" ToolTip="Edit" />

The following doesn't work in either: (why not?)

<img src="~/App_Themes/Default/images/two.gif" />

The following works in dev but not in production:

<img src="../App_Themes/Default/images/two.gif" />
asp.net image relative-path
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