As you might know, the server is protected with a whitelist to prevent random people from logging in and immediately wreck stuff. This is merely there as a deterrent, as getting whitelisted takes only a few minutes and is automated. The short version is to create an account here, confirm the received e-mail, add the Minecraft username in the user profile, and that's it. Compared to other servers, there is no manual approval of accounts required, so it's a quick process with no wait time.

The thing is, many people find this server from various lists or forums, try to access it immediately, then get kicked off with the following message:
"Get on the whitelist! See http://www.creeperslab.net/server.php !"

Short, simple, and to the point. The problem is, the large majority of those people won't even visit the page and follow the steps, so they never come back. I'd like to retain a larger proportion of these people to expand the player base, and maybe a better message would cause them to pay attention and jump in. As such, I'm turning over to you: what message should be there to invite people to join despite the minor whitelisting inconvenience? What would get their attention?

I've got 256 characters available for the message. I obviously want to include the URL with the instructions, so that brings us down to 217. Any suggestions?

Putting a username on this site is not going to stop anybody who wants to wreck stuff. The only thing it does is make sure it's a human, rather then a bot, and ensure they are willing to go through complicated procedures and/or create an account at a site they don't necessarily have interest in, in order to get on the server. Many farmers and other server-destroying people do this, so there's no reason to believe a butcher-person wouldn't be willing to. If you think you are having trouble with too many people getting kicked off the server, why not make your human confirmation easier - i.e. not involving a site - by doing it through the chat message instead? If Minecraft allows that.

The whitelist has been surprisingly effective, actually, and I would say that it's our best wall of defense. In fact, the only time we had a coordinated attack from several people is that one instance where I willingly took the whitelist check offline for a few hours...

I don't want to rely on human approval of all players as we're not online 24 hours a day, and as such many newcomers would be completely powerless for several hours... and the large majority of them won't wait that long when there are so many other servers out there. Besides, I need them to register here to properly support advanced features like the achievements.