How to send Emails from a C# Web app

Hi,
 I'm having some trouble with sending an email off my C# web app.
Its a project i have and i want to send a confirmation email to somebody who registers for my site. I'm hoping to have them enter their email in a textbox (txtEmail) and send them a simple mail from my app.
 
I've been lookin through the net quite a bit and although there is alot of info out there I am still getting errors! I think it may be to do with my SMTP (which i'm really not sure of)
here is some of the code that i've tried but errors when i play it.(I'm sure i'm way out but i'm only learning and would appricate any help. Thanks
 
using System.Net.Mail;
protected void Button1_Click(object sender, EventArgs e)
        {
            MailMessage msg = new MailMessage();
    &nb ...