This problem has existing for the last several revisions. I've commented on it since version 1.4.1, as has at least one other user.
If one monitors webpages, you have to list each ip address individually. If you try to monitor (or exclude) a range of IPs, it does not work.
I'm currently using the latest version (1.4.6).
[NG]Owner
Web Monitor Not Taking IP Ranges
Moderator: Moderators
Re: Web Monitor Not Taking IP Ranges
Sorry it took so long to get to this. I committed a fix for this issue today, so this should be fixed in the next release.