When web retailer boo.com went into receivership in May 2000, an early casualty of the dotcom collapse, the site's poor and user-unfriendly design was seen as prime culprit for the company's failure.

Boo invested heavily in a state of the art website with gimmicks such as animated sales assistants, zoom-in product views and a 3D rotating dummy to model buyers' clothes. But nobody had bothered to ask potential customers what they wanted - which was pages that loaded fast and a quick and easy ordering process. When the company collapsed, one commentator described it as 'the death of style over substance'.

Throughout the history of computing, the people who actually have to use computer systems have generally been the last to be consulted about their needs and preferences. User-testing usually occurs at the last minute, when it's too late to make major changes. If it happens at all, that is. It's often seen a luxury extra, and luxuries are the first thing to go when times are tough.

But differentiating between luxury and necessity isn't always easy. Should businesses in a recession be investing more, rather than less, in making their systems easy to use?

Usability guru Jakob Nielsen of Nielsen Norman Group argues that they can't afford not to. He claims that the return on investment from improving the ease of use of external websites is at least 760%. For internal intranets, he claims, it can be anything from 55% up to 1923%, depending on company size.

Dubious statistics aside, how well your systems work does have a direct business impact. Internally, savings come from more efficient use of employee time; from lower IT support costs; from streamlining input from information providers. Nielsen claims that improved external usability can increase sales, reduce return rate, and improve customer retention. 'You're wasting shareholders' money if you don't have good usability on your website,' he says.

With certain products, price is the main determinant of business success; with others, aesthetics are more of an issue. But as Dave Travis of consultancy System Concepts points out, fitness for purpose is also a factor in success. 'Products like websites and phones make their money from usage,' he says. So, 'if people can compose and send text message 30% faster with a given phone, they're more likely to use text messaging with it. This makes more money for network providers, which makes it more likely that providers will sell that model'.

If your company is aiming to do business over the web, then the website is your storefront. Making sure that it draws customers in and that they want to use it boils down to basic good customer service. The only real difference between a website and a bricks and mortar outlet is that human employees can use their initiative to improve on inadequate sales systems, but a website works the same way for everyone. If it's hard to use, each time a potential customer gives up on your site because they can't find what they want, that's not only a lost sale but also a waste of the money you've invested in your web venture.

Forrester Research has estimated that the costs of poor website design include losing at least 50% of potential sales. A site where customers can't find what they need will not get always get a second chance: 40% of customers never return if their first site visit was a negative experience.

'Usability is a web must-have, not a luxury, as the business success of a site is dependent on the behaviour of the users,' points out Ian Curson, usability consultant at Oyster Partners. 'If they don't like it, find it difficult to use, or don't understand the value, they go elsewhere.' Oyster's clients have included low-cost airline Go, which called it in to improve its e-commerce website. Results of the revamp included a significant rise in online sales, which now make up 70% of total sales.

Despite the dot.com collapse, web usability specialists are not short of customers. Magnus Lif, a consultant at IconMedialab (IM), thinks that three factors are responsible.

First, companies that a few years ago were desperate for any kind of web presence are now being much more discerning about where the return on their web investment is coming from.

Second, the shakeout in the competition means that remaining players are looking to improved usability as their primary way of differentiating themselves from their rivals.

Third, with more and more households moving online, the web is on the brink of becoming a genuine mass market. Almost half of UK households have now made a purchase online. And of the reasons for picking one site over another, word of mouth rates highest of all.

This generation's web buyers aren't the eager-beaver early adopters who like to use new technology for the sake of it; they're more cautious, conservative buyers who will use the web only as long as it's actually more convenient. 'Early and late adopters have different needs,' says Lif. 'The new challenge is to apply the web to late adopters.'

Improving the effectiveness of an e-commerce site need not be a major financial undertaking. According to IM, when it comes to usability improvements, even small investments can result in major payoffs.

One of IM's first steps is to check out the site by watching groups of test users try to complete certain set tasks on the sites.

When IM asked a group of users to obtain a quote from one online insurance broker, for example, it found that eight out of 10 of them gave up without ever getting the quote. Similarly, when it was called in to improve the usability of an interactive TV service, IM discovered that 18 out of 24 users couldn't figure out how to use the email facility that came as part of the service.

In both cases, fairly minor remedial work yielded significant payoff. After a redesign that took about 25 man-days in total, seven out of 10 users of the insurance site succeeded in obtaining a quote. After a redesign that took around 60 man-days, the success rate on the interactive TV email system had risen to 100%.

Even 60 days is not a long and expensive project in IT terms, and in general, improving usability isn't rocket science. Simply by observing which features of a site trip users up, where they get stuck or confused, an external or in-house usability team will be able to suggest obvious improvements.

By watching their staff working on their corporate intranet, one company realised that people were getting confused by the search feature, which originally combined people search and site search in a single box with a button to select between the two. Because the default was a people search, users trying to do a site search often ended up doing a people search by mistake. Simple solution: keep the people search and site search buttons separate - saving the company a lot of time.

There are a number of basic guidelines that, if followed, make websites and computer interfaces generally easier to use. Though when Forrester Research surveyed 20 major websites, it found that on average they only complied with just over half the guidelines.

It's best to stick to basic conventions. These include approaches such as keeping navigation down the left hand side of the page and links in blue; clear, simple labelling; being consistent about where you position basic navigation controls; and avoiding features that will only work if your site visitors have the very latest version of a specific browser.

As boo.com discovered, it's also fatal to value style over content. Those Flash animations may look impressive when the design team demonstrates them, but customers without the latest version of Flash technology won't be able to see anything at all, while others won't be happy to have to spend 10 minutes downloading them over a slow modem connection. Boo has now been relaunched and, while still bright and jazzy-looking, the tricks and gimmicks have been radically toned down.

If you want to ensure that your company's website is easy to use, it's best to start at the beginning. If the potential users are consulted before development even begins, and their input is used to drive the development, it's much easier to produce an end-result that meets their needs.

'Usability-focused work actually saves money, by avoiding the development of irrelevant features, and ensuring the offering is fit for purpose when it goes to market,' Ian Curson points out. 'This improves uptake, customer conversion rates, customer satisfaction, customer referral rates and revenue.' And a system that meets its users' needs is more likely to achieve the business goals set for it and produce a return on your investment.