You can\'t really copyright a general layout and vanilla code. How can anyone copyright something like \"margin-top: 0;\" anyway?
When people copyright websites, they mostly copyright graphics and content, with some exceptions on complex and isolated navigations.
Form follows function and there are only so many functional designs that don\'t turn visitors off. The trick is in personalizing it with your own unique feel.
It\'s very hard, expensive and time-consuming to prove in court that someone has stolen your layout. I remember Apple tried to sue someone for ripping off their layout and lost.
Most of the cases I\'ve come across where someone was successful in persuading another site to change its layout (because presumably it looked too much like a copy of another site) is by directly e-mailing the owner, sometimes even with threats of taking legal action. But if they were to actually take that person to court, they\'d be hard-pressed to make a case.
Now, that doesn\'t mean it\'s ok to blatantly rip famous sites off. Don\'t copy/paste lines of code, and definitely don\'t rip off graphics and text content. That can be proven in court to be stolen and you can get in trouble.
There are also templates that more than a single person can buy from places that sell such templates. People that use the same WYSIWYG programs can end up with similar code too.
You have to realize though that every web designer/developer has learned from publically available examples and others\' work. That\'s not considered a rip off. People also get inspired by well designed sites, and that\'s normal. Even most popular sites\' designers probably got inspired by something/someone else.
Basically, the advice is
\"copy the inspiration, not the outcome\".
Read this article titled
Good Designers Copy, Great Designers StealEverything you see on the net and even in pure art and design is a variation of something that came before it. So, complete originality is overrated and can even ruin your success.
Pretend that a site you got inspired by is yours. Then compare it to what you consider a similar one. Does it make you angry? Is it an obvious and blatant rip-off or just an inspiration? If your reaction is \"ah, yes, I love clean layouts like that\", then the site is fine. But if it\'s \"how can this person sleep at night?\", then it\'s probably stolen.

You\'d be surprised though how many sites get posted at \"pirated-sites\" website with someone screaming \"stolen!\" and yet get voted as \"No - not stolen\" by majority.
What are those site you saw that stole PlaneShift\'s layout anyway? Post some links, so we can see.