Other sections of the style guide have dealt with the layout and structure of text. Here I digress to broaden the notion of style into a consideration of what is acceptable in the actual content of information put on the web.
The web is intended to be a mapping of the knowledge of society in general, and not constrained into a particular format or level. One can therefore expect to find anything on it, from scribbled note to encyclopaedia, and styles and manners will vary. However, for information which is to be generally accessible there are some questions of acceptability which apply simply because the material has been published.
There is a tendency on the Internet to regard news and email as very informal media, in which tolerance is expected. However, you never know who may link to or be led to your public web document. In some countries there may be legal requirements as well as informal ethical codes. I would not advocate any global censorship in this regard, but that does not mean you should not think about which aspects below are relevant to the document you are writing.
The visibility of someone's work depends, on the web more than anywhere, on where it is referenced. If an academic paper purports to be a description of some state of affairs and in fact does not mention related work which maybe of interest, the academic code requires that you refer to it.
Commercial servers selling products are not in practice bound by such a code: you don't find hypertext links to competitor's products. Therefore, make it clear whether your list of services is intended to be fair, or is commercially biased. Both forms are appreciated by the public, but an advertisement masquerading as something else is not.
Pornography is just the most often discussed form of content which is generally disapproved of and illegal. There are others: libel, material infringing copyright or other intellectual property right, and material inciting to criminal activity are also things which you would be wise to avoid. Bear in mind in this context
and try not to upset any of them.
Where you feel that something may offend your reader, you can to a certain extent protect both yourself and them by making an access path which goes through a warning page, and never yourself distribute URIs for anything behind that page without a similar warning. This is not, of course, foolproof.
The PICS initiative of the W3C consortium is aimed at allowing you (or anyone else) to rate your pages as to their acceptability. The idea is that parents and schools can then use rating systems of their choice to select suitable content for their children. This technology is expected to be available commercially some time in 1996.
Unacceptable language is the simplest form of unacceptable content. Standards tend to vary from one country to another: in the US they are high. Here is a non-exhaustive non-definitive checklist of a few sorts of language to avoid.