Global variables can be set in web.config. In general, these are variables that are not frequently changed. For example, the mail server. A key can be added in the
<configuration>
<appSettings>
<add key="MyMailServer" value="mymailserver.com" />
</appSettings>
</configuration>
Then the value can be retrieved in the code
Dim MyMailServer as String = ConfigurationManager.AppSettings("MyMailServer")