You can use this code to save the screenshot when there will be any possibility of error in the application .If the client is using the application developer can ask the client to send the screenshot so that he can know in which page the error was occured
To take the screenshot
Bitmap bitmap = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height);
Graphics graphics = Graphics.FromImage(bitmap as Image);
graphics.CopyFromScreen(0, 0, 0, 0, bitmap.Size);
bitmap.Save("c:\\screenshot.jpeg", ImageFormat.Jpeg);.