1.) R-E-S-P-E-C-T...
That's right, rule Number 1 is Respect. If you don't show respect to others, they have every right no to have respect for you. This is especially important because it is the internet, and as simple mis-placement of words can dramatically change the meaning of what you say.
2.) Offensive Materials...
Nothing illegal (Warez, Torrents, Copyrighted Items), pornographic, or excessivelly violent.
3.) Spamming & Digging...
No spamming of advertisements or double-posting. Also, no digging up old topics and posting in them unless it is to add something, eg: extra blueprints, corrections.
