How do I restrict access to a domain by IP?

Introduction

How can I allow or deny access for a domain from an IP address? 

Procedure

You can utilize the 'deny from' option within your .htaccess file. 

As an example,

deny from 192.168.168.10
deny from 192.168.168.20

If you want to block an entire range, you can either use CIDR or remove the last octet.

deny from 192.168.1

or something like:

deny from 192.168.1.0/24

If you wanted to block everyone but the IPs listed, you could use:

deny from all     
allow from 192.168.1.0/24