This part of ISO 9241 provides guidance on the human-centred design of software Web user interfaces with the aim of increasing usability. Web user interfaces address either all Internet users or closed user groups such as the members of an organization, customers and/or suppliers of a company or other specific communities of users.The recommendations given in this part of ISO 9241 focus on the following aspects of the design ofWeb user interfaces:. high-level design decisions and design strategy;. content design;. navigation and search;. content presentation.The user interfaces of different types of user agents such as Web browsers or additional tools such