Hi, Ilegal webpages webmaster-client relation

Does anybody knows how much the webmaster is involved in a webpage creation, talking about legal and ilegal use ?

That depends on the country and the law. If you are an accomp. then yes. If somone tells you he needs a webdesign and you create it and he pays, but if he uses it afterwards then you are free to blaim.

It is also hard to proof. Why planning something illegal

It depends on what's illegal and your reasonable culpability and role which actually is a terribly complicated matter. Assuming this is US law ...

If your work entirely enabled felonious criminal activity, for example a site which serves as a dispersing point for photographs of underdressed, underage models then you may be implicated in part because of the extent of the laws behind the activity itself. On the other hand, if you merely put together a PHP photo album and chat room that was later used for this purpose but you had no knowledge of this use then you'd be cleared.

My advice would be to steer clear. If you're asking, there's something fishy and I don't think lemon and malt vinegar will go well with whatever it is.