I have discovered that Answers.com improves on this with a rather nifty hidden feature: if you double click on any word on the page it will immediately look that word up in Answers.com using AJAX!

This looks very innovative to me. Using the rich Javascript API to augment the browser's existing functionality is very pleasant, but here the product is a dictionary/reference site that is totally cross-linked! Poor old Wikipedia seems rather limited by comparison (though, to be fair, there are massive advantages to conventional links. This technique is not a replacement for that).

On the other hand, website owners do not want their image damaged by users who can't keep their potty mouths shut.

When developing sites that allow users a voice, we need to find ways to protect the website owners, or the atmosphere of a community, without damaging the goodwill of the user base. Any website that depends on user input, and which doesn't have any users, is a failure.

Profanity filtering is not the answer because, at least, I've never seen it done well enough to be both comprehensive and unintrusive. All problems that relate to processing natural language are extremely complicated. We have barely started to scrape the surface in terms of parsing English text, let alone extracting the semantics from it that we would need to determine if a word is offensive. So any attempt at a naïve profanity filter is doomed to failure. For example, you can be profane without being offensive:

She turned round and screamed, "Fuck off, you stuck-up bitch". I was appalled!

You're a grumpy old bastard, but I love you.

and you can be offensive without being profane:

I did your mum last night. She's fatter than a blue whale, but she knows a trick or two. Your sister does too actually.

and let's not forget the cases where you can't tell:

Do you have a cock or do you just keep hens? Oh, we have a big gold cock. You know, the pussy is afraid of him!

Ok, the last example is contrived and of course nobody would type it with a straight face.  Still, in the right context, it's innuendo not profanity.

With those insurmountable problems, there's simply no substitute for a human keeping an eye on things. However, even with moderation, there are problems to face. Exactly what is acceptable? Moderators can easily pronounce on clear-cut cases of abusiveness or offensiveness, but people have different sensibilities as to what's acceptable. It's also fairly easy for moderators to miss the odd bit of abuse, especially if it's only offensive in some contexts.

One trick to help keep control of the situation is to carefully set the tone. If you can use the language and style of the website to convey a sense of what might be appropriate, you can influence the tone users are likely to take. Though moderators still have to check the same amount of content, this reduces the chance that something untoward will slip through. Phrases like "Interglobal Inc do not take any responsibility for the content of this service"  – phrases which are of dubious merit anyway – may have the opposite effect, by giving users the impressi0n that they don't care what the tone is. You also stand to lose control of the tone in the subconscious minds of users if you use some well-known software – phpBB for example – which users might have used elsewhere and come to associate with a certain mode of speech.

If you do censor people,  a light touch is often better than a heavy hand.

However, in practice these editors become incredibly painful to use. When you watch users trying to edit a content management system, it becomes very obvious that the usability they profess is an illusion.

• The editing experience is slow, sometimes to the point of non-interactivity
• Loading of the component is also slow
• Users struggle to make formatting behave when all they want to do is write
• Pasting from word processor documents also pastes unwanted formatting

My solution is to return to the humble textarea. This was something I discovered by accident: Django provides a Markdown filter, so this was the simplest way to provide formatting, though my intention had been to embed TinyMCE later. Markdown is a simple formatting language based on formatting conventions in plain-text e-mails. I soon discovered the convenience of editing content with Markdown – freed from worries about formatting, the experience of publishing content accelerates, at the expense of a slightly steeper learning curve. It's only a learning curve for the formatting features. In the simplest case of unformatted paragraphs, writing in Markdown is the same as writing in plain text, so users can start publishing at full speed straight away.

There's also the benefit that Markdown doesn't give users the ability to break out of the style of a site. Users are not graphic designers: if you give them the ability to make text red, thinking perhaps that this may be useful on special occasions to draw attention to an important message, don't be surprised if they make every other sentence red, bold and italic. After all, they want to draw attention to everything they say, don't they?

To enhance the experience in my applications, I've bolted on a toolbar based on Livepipe and a preview based on Showdown.

Screenshot of my MarkdownArea

The practice of including calls to action is taken straight out of the advertising industry. Advertisers have a small list of things that they need to include in an advert, and a call to action is on that list. However a website is not an advert. Users browsing the web are mainly in a mode where they will read and compare and research a purchase. Who would click the first "buy this now" button they see when they can hop onto another site and check out alternatives and price first? In this context, calls to action may not be very effective and can be intrusive. It's even less effective if your call to action is not something as passive and easily handled over the web as just "buying", such as "Enquire now about our calibration service".

In the UK we also like our calls to action implicit. Watch TV ads for a few minutes and the number you'll see that include an explicit call like "Sofas half price at DFS until Monday! Come down to DFS showrooms today!" are small compared to the number that run more along the lines of "The sun is shining and this man in trendy clothes is laughing with a group of attractive women. What's that he's drinking? Oh, Coca-cola."

So include calls to action, make sure they are seen, but keep them understated and out of people's faces and users may find your site that much more appealing – easily enough to outweigh the effectiveness of intrusive calls to action.

A lot of web usability is common sense, but when you compile all that common sense into a book, it's an extremely valuable reference.