Web usability is an approach to make web sites easy to use for an end-user, without requiring her (or him) to undergo any specialized training.
The user should be able to intuitively relate the actions he needs to perform on the web page, with other interactions he sees in the general domain of life e.g. press of a button leads to some action. The broad goal of usability can be:
Present the information to the user in a clear and concise way.
To give the correct choices to the users, in a very obvious way.
To remove any ambiguity regarding the consequences of an action e.g. clicking on delete/remove/purchase.
Put the most important thing in the right place on a web page or a web application.
As more results of usability become available, this leads to the development of methodologies for enhancing web-usability.
In the context of websites, the meaning of web-usability is narrowed down to efficiency: triggering sales and/or performing other transactions valuable to the business.
Web usability received renewed attention as many early eCommerce websites started failing in 2000. Whereas fancy graphical design had been regarded as indispensable for a successful e-business application during the emergence of internet in the 1990s, web-usability protagonists said quite the reverse was true. They advocated the KISS principle, which had proven to be effective in focusing end-user attention.