Web Site Usability

What is it?

It is a quality attribute that assesses how easy user interfaces are to use. Also refers to methods for improving ease of use during design process.
Usability has five quality components:

• Learnability: How easy is it for users to accomplish basic tasks the first time they encounter the design?

  
  

• Efficiency: Once users have learned the design, how quickly can they perform tasks?

  
  

• Memorability: When users return to the design after a period of not using it, how easily can they reestablish proficiency?

  
  

• Errors: How many errors do users make, how severe are these errors, and how easily can they recover from the errors?

  
  

• Satisfaction: How pleasant is it to use the design?
  

How is it identified and or used within the development of a website lifecycle?

Get any 3 to 5 users and ask them to perform representative tasks.
Observe how users react and analyse their success or difficulties.
It's important to test users individually and let them solve any problems on their own. If you help them or direct their attention to any particular part of the screen, you have contaminated the test results.

What are the benefits of conducting usability tests and to whom are the results beneficial and why?

On the Web, usability is a necessary condition for survival. If a website is difficult to use, people leave. If the homepage fails to clearly state what a company offers and what users can do on the site, people leave. If users get lost on a website, they leave. If a website's information is hard to read or doesn't answer users' key questions, they leave. Note a pattern here? There's no such thing as a user reading a website manual or otherwise spending much time trying to figure out an interface. There are plenty of other websites available; leaving is the first line of defense when users encounter a difficulty.