First off make sure you have the key in the correct place:-
VB Code:
<configuration>
<appSettings>
<add key="AppName" value="whatever" />
</appSettings>
<system.web>
rest of web.config as normal.....
Now declare string variable in your page class and get the value:-
VB Code:
Public Class WebForm1
Inherits System.Web.UI.Page
Public AppName as String = ConfigurationSettings.AppSettings("AppName")
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
etc.....
Finally your html will look like this:-
<title><%=AppName %></title>