The logic in your code does not look right
On the button click you are redirecting the url to ImageUpload.aspx?imageCode=10 (assume the ID as 10) and this does not know anything about the javascript / the function
basicPopup()
to be called. so obviously the javascript would not get called
1. you have to amend the button so that it know that the javascript to be called on the button click
<asp:Button ID="Button1" runat="server" onClientClick="basicPopup();" Text="Button" />
This line of code says that on the buttn click the javascript to be called
2. Now move on and define your javascript
<script type="text/javascript">
function basicPopup() {
var imageCode = document.getElementById('holdValue');
popupWindow = window.open("ImageUpload.aspx?imageCode=1", 'popUpWindow', 'height=300,width=600,left=100,top=30,resizable=No,scrollbars=No,toolbar=no,menubar=no,location=no,directories=no, status=No');
//popupWindow = window.open("ImageUpload.aspx" , 'popUpWindow', 'height=300,width=600,left=100,top=30,resizable=No,scrollbars=No,toolbar=no,menubar=no,location=no,directories=no, status=No');
}
</script>
This should work
The only reson, it may not work is that you have your javascript section in a wrong place. If does not work let me know with the description of area where you have defined your Javascript