i want to show different images on a href link on sampe page

function showDiv()
{
document.getElementById('showpic').style.display = "block";

}
-----------------
<div id="showpic" style="display:none;" ><asp:Image ID="Image1" runat="server" ImageUrl="~/images/CM-06.png" /></div>
i want o n every click of a href thre should come a different img
---------------------------how can i do this??????????//