string thisUrl = app.Request.Url.ToString().ToLower();
if (thisUrl.Contains("http://www.informarea.it/BlogEngine"))
{
    HttpContext.Current.Response.Status = "301 Moved Permanently";
    HttpContext.Current.Response.AddHeader("Location", 
               thisUrl.Replace(
                        "http://www.informarea.it/BlogEngine", 
                        "http://www.informarea.it"
               )
   );
}