WWWServer supports IP-based access control, based on IP masks. Such mask consists of an IP address, where you may replace one or more of the four numbers with an "x" character as a wildcard.
The interface should be self-explanatory. Click "Add" to add a new rule, click a rule, edit it and click "Update" to change a rule. Click a rule and then "Remove" to remove it.
The list is read from top to bottom. The following setting will only allow the host "127.0.0.1" to retrieve web pages:
x.x.x.x Deny 127.0.0.1 Allow
When no rule applies to a certain host, it is blocked. Therefore, in the example setting above, the first rule is obsolete.