Effective interfaces have highly visible features and "forgive" mistakes, giving the user a sense of mastery. Users can quickly understand the options available, immediately pick up how to find the results they are looking for, and complete their navigational tasks without difficulty.

Efficient interfaces do not force the user to make an extra effort to understand the system's internal mechanisms. Here, then, are some of the basic principles I bear in mind when designing and preparing user interfaces:

Recognisable design

One aspect that must not be neglected when constructing a user interface is to guarantee that the user will always be able to identify the site; users may access the resource via external links, without necessarily knowing where they have ended up. Each page should contain all the necessary references so that users can find their way around.

Accessible design

A web page is potentially accessible to a very diverse audience, demonstrating cultural, economic, technological and physical differences. Failure to take such differences into account will prevent large groups of potential visitors from making use of the resource.

Navigable design

It is very important to construct interfaces in such a way that the user can create a mental model of the site. To make such a structure possible, it is necessary to give users the necessary navigation tools. Basic as this may sound, it is nevertheless extremely important that each page should contain a link to the home page, an overview of the site structure, and links to the most important resources.

Predictable design

Predictable doesn’t mean boring where design is concerned: it means allowing the user to predict the results of an action. Inserting a link to a Word (.doc) document may be useful, if the user is informed that they are about to open a page in Word rather than a web page. In the general principles of usability, emphasis was placed on visibility, which is closely linked to that of predictability: an object is clearly visible when the user can deduce its potential, work out how to use it and predict the effects.

When a user clicks on a link, they expect to be taken to another web page. The technological potential of hypertexts, however, makes other actions possible. They could find themselves downloading a document, a programme or an audio file, for example. A single click could cause someone to add a product to a basket when they are shopping, or reply to a survey. These are all perfectly legitimate possibilities, even from the usability point of view, as long as the user is informed of what will happen when they click on a link.