I made this similar to xDaeMoN's Join Counter (Nick Based) script except this one is address based.
Ok I decided to add a few new things, 3 new things to be exact. I would like to thank Napa for the 3 things I added and from his Greet Counter script. (Hope you don't mind Napa. =x). I also decided to make the script less annoying. Instead of msging the channel it will notice the person of what number they are and welcome them back with that same number. I also edited the "CONGRATS" part to where when the counter reaches 20 it will notice the person that they are number 20 and will msg the channel that they have gotten their 20th visitor it will also msg the channel when they have their 50th visitor and so on. This script should be easy for even new scripters to understand since it is quite simple (maybe not the $qt part but you can look it up in the help file >.>) Just copy and paste this into your remotes and you're good to go. :)

I would actually like for my script to be "RATED" this time. -_- The comment part is for commenting the script not for telling me what you "would" rate it and "not" rate it anyway. So again. Rate people! Please and thank you. :D

on *:start:{ if (!$hget(Greetdata)) { hmake -s Greetdata 200 | hload -s Greetdata $qt($scriptdirGreetdata.hsh) } }

on *:JOIN:#: {
  if ($hget(Greetdata,$address)) {
    notice $chan 9Welcome Back $nick $+ , visitor $chr(35) $+ $hget(Greetdata,$address) ! :D
  }
  else {
    inc %counter 1
    hadd Greetdata $address %counter
    notice $chan 9Welcome to $chan $+ , $nick $+ ! You are visitor $chr(35) $+ $hget(Greetdata,$address) ! :D
    .timer 1 2 hsave -a Greetdata Greetdata.hsh 
  }
  if ($right(%counter,2) == 00) || ($right(%counter,2) == 50) || (%counter == 20) {
    hadd -s Greetdata $address %counter
    describe $chan shoots fireworks for4 $nick *~~~~~|#####> `';:*,.,*:;'`12 $nick *~~~~~|#####> `';:*,.,*:;'`9 $nick *~~~~~|#####> `';:*,.,*:;'`7 $nick *~~~~~|#####> `';:*,.,*:;'`13 $nick *~~~~~|#####> `';:*,.,*:;'`11 $nick *~~~~~|#####> `';:*,.,*:;'` 
    msg $chan 4,12CONGRATS, $nick $+ !! You are the $ord(%counter) vistor to visit $chan $+ !
  } 
}
on *:disconnect:{ hsave Greetdata $qt($scriptdirGreetdata.hsh) } 
on *:exit:{ hsave Greetdata $qt($scriptdirGreetdata.hsh) }