<add key="SMTP" value="smtp.gmail.com"/>
<add key="AnnouncementEnabled" value="true"/>
..........
</appSettings>
later you can use those settings where appropriate.
the following shows how to access those settings
in code behind file of any asp.net pages -
first include using System.Configuration; to
use ConfigurationManager class.
//the codes to access settings
string smtpHost;//host for sending emails from .net
smtpHost =ConfigurationManager.AppSettings["SMTP"];
if (Convert.ToBoolean(ConfigurationManager.AppSettings["AnnouncementEnabled"]))
Announcement.Text = ConfigurationManager.AppSettings["Announcement"];
else
AnnouncementPlaceHolder.Visible = false;