In my opinion, a usable Web site is one which:
- can help users to achieve a goal (usually, to obtain some information or "do something" such as ordering a book)
- makes it easy for them to achieve that goal
- allows them to achieve it quickly
- gives a pleasant (i.e. not boring or painful) experience while the goal is being achieved
I wrote that list roughly in order of priority (most important to least). Some sites may have different priorities.
Many of the techniques discussed previously help to achieve those criteria. To give specific equivalents to the above list, a site is probably usable if:
- the content is worthwhile
- it is easy to find desired information within the site
- pages download quickly and there are not too many "clicks" between the front page and a target page
- the page is pleasantly, cleanly designed
Worthwhile content
To be usable, your site must do something useful - provide information or services that will be of interest to your audience.
For example, users heading to an electronics manufacturer's site are likely to have one (or both) of two goals in mind:
- information about products
- chance to buy products
If it is not possible for a site to include content which users will want, then a site can still achieve usability by wasting as little of the users' time as possible - in other words, by making it clear and obvious from the very start that the desired content is not present.
Making it easy
Pages can make it easy to obtain content by providing good navigation controls, and helping the user to understand the navigation scheme with location information etc.
Considering the different types of users your site might have (especially their levels of experience) can help you determine how best to design controls suitable for those users. For example, inexperienced users may need more explanation while experienced users might understand common Web concepts like "home", "up", "shopping cart", etc.
Making it quick
There are two main ways to make a Web site quick to use:
- Making pages download quickly
- Designing the site so that users can get to a desired page quickly
You can make pages download quickly by being careful with image sizes, and carefully balancing page size against the number of pages (e.g. making an appropriate decision about where to split information into multiple pages).
Allowing users to get to their desired page quickly is less simple, but usually more important. Here are two strategies.
- Consider each group of user, figure out which pages or sections they will most likely want, and feature these prominently from the site's front page
- Make sure that pages contain sufficient navigation so that users can get directly to other pages they want from within the site (but not so much navigation that users will be confused)
Clean design
Clean design can make pages more pleasant to look at, and also easier to use. You don't need to be an expert graphic designer to create cleanly-designed pages.
- Avoid unnecessary elements (graphics or text that isn't relevant)
- Avoid distracting elements (animated GIFs, striking colours, etc.) that don't have a clear purpose
- Don't use techniques you don't understand (e.g. if you are not confident of your colour design skills, stick to very basic colours based around black on white)
- Arrange the page into visual areas (title, content, navigation, references, etc.) and stick to that template
