When we publish a web site is important specify an alternative server to manage the exceptions when one, or more, servers are not available. In Kemp LoadMaster this feature is called Sorry Server or Not Available Server. To set this, is necessary open the Virtual Services and add the IP Address into Advanced Proprieties area, as showed in figure 1.
After this, you can test the web site disabling all the Real Servers, as showed figure 2.
The result should be similar like figure 3, depends by your page.