More than one web server is trying to listen on port 80.; MarkVision Professional (MVP); Microsoft Windows NT4 server; Microsoft Windows Server 2003; Microsoft Windows 2000; Microsoft Windows XP; This error occurs when MVP is trying to listen to a port which is being used by another web server. (The default port is 9180, but this can be changed in MVP.) If another web server is listening on the same port as MVP, MVP server will not be able to start until the other server is shut down.
To resolve this issue, you can either disable the other web server, or else set MVP web server to use a port other than port 80. For instructions on how to change the port in MVP, click here.