failed to redirect to another page.

Question

Can someone tell why the code below failed to redirect to the specied URL? The front-end of this code resides inside a tab container. Could it be the reason why it failed to redirect?

string message = "New motor policy " + motorpolicy + " has been successfully saved.";
                    string script = "window.onload = function(){ alert('";
                    script += message;
                    script += "');";
                    script += "window.location = '";
                    script += ResolveUrl("../d-Underwriting/Motor/CheckCustomerMotorDataEntry.aspx");
                    script += "'; }";

                    ClientScript.RegisterStartupScript(GetType(), "SuccessMessage", script, true);