QUOTE(LamontStormstar @ Wed 3rd January 2007, 1:17pm)
ISPs that change IPs only change the last bit of numbers or so.
An IP address consists of four numbers, e.g. 102.35.245.85; none can exceed 255. If you get a new address from the same ISP, the fourth number will often be completely different and the third may change appreciably. It is possible for an admin to block a range of IP addresses; for example, blocking 102.35.0.0/16 will block all IPs with the first two numbers. This is unlikely to add to the gaiety of nations, as no doubt several innocent users will get blocked too.