These days, usability is a deciding factor in the development and design of software and Internet applications. However, functionalities in the system do frequently exist, but cannot be used or used properly by users because of their operation is too complicated or users are unable to find certain functions.
Usability is a term that generally defines the ability to use a product or service. According to the International Organization for Standardization (ISO), usability is defined as the extent to which a product can be used by certain users in order to attain certain goals effectively, efficiently and satisfactorily in a specific usage context [TA08, page 4]. Consequently, the suitability for certain uses and hence the compatibility of a system within the context of usage, is defined in a specific user context.
Jakob Nielsen  lists the following objectives as the benchmark for the quality of user interactions with a system:
• Learning ability: It should be as easy as possible to learn how to use the system so that assignments can be handled as quickly as possible.
• Efficiency: The system should be designed for the efficient use of time and allow for a high degree of productivity.
• Ability to recall: It should be easy to remember how to use the system so that once the user comes back to use the system he or she does not have to relearn its utilization all over again.
•Errors: The system’s error rate should be low.
• Satisfaction: Using the system should be convenient in order to ensure user satisfaction.