If your application uses forms-based authentication and unauthenticated users try to access a protected page, then they’ll be redirected automatically to a login page. By default this is Login.aspx. However, you can specify a different login page by setting the loginUrl attribute in the forms section of your web.config, shown here:

<system.web>
  <authentication mode="Forms">
    <forms loginUrl="~/customLogin.aspx"/>
  </authentication>
</system.web>

Once logged in successfully, users will be redirected to Default.aspx. You can specify a different page using the DestinationPageUrl property of the Login control:

<asp:Login id="Login1" runat="server" DestinationPageUrl="welcome.aspx"/>

You can also set this in web.config using the defaultUrl attribute:

<system.web>
  <authentication mode="Forms">
    <forms defaultUrl="~/welcome.aspx"/>
  </authentication>
</system.web>