You can add web-server address, as new device. DNS address of the web-server.
Then modify Device settings, right click on the device set 'address to name'.
Addresses DNS names, lookup, lookup interval: device address information. A set of IP address and DNS names may be assigned to a device. Either primary IP address (lookup=name to address) or primary DNS name (address to name) is resolved regularly (with the given interval) from the other.
Set DNS address that you want to monitor and set HTTP service.