Add semicolon (i.e. ;) after
alert
statement, update it like below:
ScriptManager.RegisterStartupScript(this.Page, base.GetType(), "Message", "javascript:alert('" + message + "');", true);
i believe your script is throwing an exception and because "Disable script debugging" is checked in IE you are not getting any notification.
Hope this will help.
Thanks,
Hemant