What is the best way to display error/warning messages on website app?

Question

I'm creating a website app(ASP.NET, C#) and I just want to know the best way to display error/warning messages. Is it better to do it by MessageBox or thru a Label? Just need some suggestions.

Answer 1

I would prefer to do it in this way:-

 this.RegisterClientScriptBlock(typeof(string), "key",  string.Format("alert('{0}');", ex.Message), true);

Answer 2

For server side validation, you can write a custom control (which I did) like this to display message consistantly through out the site.

For client side validation, you can use validation summary.

<asp:ValidationSummary ID="ValidationSummary1" runat="server" DisplayMode="List"
    ShowMessageBox="true" ShowSummary="false" />