Grafic Interface and test of efficience

The norm ISO 9241 says that the usebility is “the grade with whom a product may be used by particolar users to reach some goals with efficacy, efficiency and satisfaction in a specific use context”

For example, usually a software is used after have bought it; a web site is first of all used and only if it is satisfying, it will be used for a transaction and eventually gives profits.

It means that for software the usebility is not an important matter for profits; but it is really determining in web site, because it is preliminary condition to reach profits.