Change your javascript
function display() {
alert("Program Has Been Successfully Create");
if (confirm("Do you want to create phases?") == true) {
window.location = "CreateProgramPhase.aspx";
}
else {
window.location = "CreateProgram.aspx";
}
}
</script>
and change button click event as
protected void btnSave_Click(object sender, EventArgs e)
{
AddProgram();
if (ClientScript.IsClientScriptBlockRegistered("test1212") == false)
ClientScript.RegisterStartupScript(this.GetType(), "test1212", "<script>display();</script>");
}