Kathy Sierra at CPU wrote a piece last week called How to get Users to RTFM. From the source:
Make Reading the Manual Unnecessary
In theory, "If your product is good enough, they shouldn't need a manual." In practice, that's a meaningless sentence without context. If your car radio does need a manual (oh, how I hate that mine does), blame the designers. But if your pro video editing software doesn't, then it's probably not a "pro" app. A complex product that needs a manual does not necessarily mean there's a design flaw.
Since Kathy's writing for a broad audience, I think this statement is perfectly apt. However... If you're architecting, designing, developing or testing a website, specifically, then Kathy's theory should be a universal truth, interpreted as:
No website or portion of a website should require instructions of any length.
I'm almost loath to give an exception, but there are two - if you have a Flash or Java application (like a game or quiz that has rules and requires the use of keyboard buttons) you may give brief insructions - i.e. jump over the turtles with the ctrl button, shoot lasers with the space bar. Instructions can also be applied to complex forms (like the IRA online tax filing system - not your e-commerce checkout).
In any other case, instructions are:
- A waste of your time
- A waste of your visitors' time
- A waste of screen real estate
- Inhibiting your site's usability and user experience, leading to fewer links and fewer visits
- Useless to search engines
- Already far too common
One of the biggest problems is that website creators often don't even realize they have instructions on their site. For example, just check out the Rock & Roll Hall of Fame:
Those "requirements" and that "enter" button are instructions. Obviously, a splash page, non-cross browser compliance, and the use of Flash without an auto-detect system are already pretty bad, but it serves as a good tutorial. Visitor flow should be so easy and seemless as to be unnoticeable. Great navigation goes completely unrecognized, just like so many parts of great design in the physical world.
BTW - I recommend reading CPU every day. Their posts are solid gold and consistently interesting, well-documented, and cleverly illustrated.
p.s. - This week is a complete nightmare with interviews today: Thursday and Friday (for our new position), an all day trip Wednesday to San Francisco (for some consulting), and late evening meetings/parties tonight, Thursday, and Friday. If you see me blogging before Saturday, consider it a miracle. 
Rand, for your next post, can you give us a full list of all the blogs you read? I need some more gems like this one!
Actually, I did a post on that just recently - https://www.seomoz.org/blogdetail.php?ID=1286
Doh! So that just proves that I already have to much to read in any given day. But I will still end up subscribing to every blog on that list that I don't already. Man I love this job.
It's impossible to be 100% sure whether instructions are good or bad. You're right though, that site's should seriously think about the instructions they are giving their users. Even as a coder, I HATE going to web sites that require too much work to get to their most important parts. Yours, for instance, required me to sign up before I could leave you a comment. Irritating...just like members only sites like MySpace and MadeBig. The entire experience is just a bunch of instructions telling you what and when and how to do things in order to accomplish your most simple goals. I almost forewent publishing to your comments just because of the principle of the matter but I decided it was worth a moment to tell you that you're doing what you loathe. I disagree that a complex item should need a manual. There's no reason for something to be complex. Say for example, you need to create a mask in Adobe...you shouldn't HAVE TO HAVE the instructions pop up in front of you every time you use that feature...there's a tutorial. Have it there for people to access if they WANT TO...but don't FORCE them to have it. Shouldn't it really all be user driven, and NOT designer driven???
If you need to add an instruction a tiny little ? icon and an onmouseover hover box works perfectly.
I actually do like those a lot. Not always for instruction, but particularly if you're looking at complex information in a form, chart, graph, or visual display, those hover boxes rock. Good call, mad!
Sounds a lot like the 'don't make me think' principle. Ideally a user should know exactly what to expect when they click a link. Worst case they should pause and get a little thought bubble that says "hmm I wonder if this will do A or B". If they have no idea what will happen or what's on the other side of the click then you failed your job.
Jonathan those sites you're referring to can not be compared to standard websites. Digg and other social network websites have their own functionality and for it to work (since most of it depends on it's visitors), they do need to give instructions.
When it comes to e-commerce sites or websites that are in a competitive environment, there should not be an "instruction message on the home page"
I agree Igor. In fact that's exactly the point I was trying to make. The web and user experience engaging with it are not one size fits all. Especially as we move forward with more interactivity and new ways of using the web we should be careful about generalizations. After all, the very idea of a "site" is so 1.0... isn't it? :)
Websites are different than other products because the first time you use them they're running with all the bells and whistles going at once. It's like if I bought a car stereo and right when I turned it on it was blasting Massive Attack - Safe From Harm and a dolphin was swimming across the display. Because of that, websites uniquely have to be functional right from the start, which is a concept most non-designers/developers have a hard time with.
That isn't to say that all sites are understood 100% right from the beginning. The first time I went to Digg, I had no idea what was going on. What do those number mean? Dugg? What the crap is that? Or take NewsVine. Unless you know what it's all about, the site looks like your basic news site, but there is so so much more going on.
I think the moral of this comment is...make a website functional without a manual -- that is to say, allow people to navigate and read content without much effort to get to see what the want to see -- but still offer some sort of "so what am I looking at here exactly?" style of documentation.
There are a few sites that require instructions for newbies that have become very successful including Digg, Flickr & Delicious.
I think that Flickr has instructions if you want to use their application to host your photos, but Digg & Del.icio.us are pretty plug and play, though I'd say that Del.icio.us in particular could use some help as newbies who get there will probably have a very tough time.
Wikipedia has instructions, too - but they're only there for folks who want to use the application, rather than just for people who want the content :)
Great points, though. I think Skype would be another that does require instructions...