SIST EN ISO 9241-151:2008

SLOVENSKI STANDARD
SIST EN ISO 9241-151:2008
01-september-2008
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Ergonomics of human-system interaction - Part 151: Guidance on World Wide Web user
interfaces (ISO 9241-151:2008)
Ergonomie der Mensch-System-Interaktion - Teil 151: Leitlinien zur Gestaltung von
Benutzungsschnittstellen für das World Wide Web (ISO 9241-151:2008)
Ergonomie de l'interaction homme-système - Partie 151: Lignes directrices relatives aux
interfaces utilisateurs Web (ISO 9241-151:2008)
Ta slovenski standard je istoveten z: EN ISO 9241-151:2008
ICS:
13.180 Ergonomija Ergonomics
35.240.99 8SRUDEQLãNHUHãLWYH,7QD IT applications in other fields
GUXJLKSRGURþMLK
SIST EN ISO 9241-151:2008 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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EUROPEAN STANDARD
EN ISO 9241-151
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2008
ICS 13.180; 35.240.99

English Version
Ergonomics of human-system interaction - Part 151: Guidance
on World Wide Web user interfaces (ISO 9241-151:2008)
Ergonomie de l'interaction homme-système - Partie 151: Ergonomie der Mensch-System-Interaktion - Teil 151:
Lignes directrices relatives aux interfaces utilisateurs Web Leitlinien zur Gestaltung von Benutzungsschnittstellen für
(ISO 9241-151:2008) das World Wide Web (ISO 9241-151:2008)
This European Standard was approved by CEN on 8 May 2008.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9241-151:2008: E
worldwide for CEN national Members.

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EN ISO 9241-151:2008 (E)
Contents Page
Foreword.3

2

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EN ISO 9241-151:2008 (E)
Foreword
This document (EN ISO 9241-151:2008) has been prepared by Technical Committee ISO/TC 159
"Ergonomics" in collaboration with Technical Committee CEN/TC 122 “Ergonomics” the secretariat of which is
held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by November 2008, and conflicting national standards shall be withdrawn
at the latest by November 2008.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 9241-151:2008 has been approved by CEN as a EN ISO 9241-151:2008 without any
modification.

3

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INTERNATIONAL ISO
STANDARD 9241-151
First edition
2008-05-15


Ergonomics of human-system
interaction —
Part 151:
Guidance on World Wide Web user
interfaces
Ergonomie de l'interaction homme-système —
Partie 151: Lignes directrices relatives aux interfaces utilisateurs Web




Reference number
ISO 9241-151:2008(E)
©
ISO 2008

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ISO 9241-151:2008(E)
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ii © ISO 2008 – All rights reserved

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ISO 9241-151:2008(E)
Contents Page
Foreword. iv
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Application . 6
5 A reference model for human-centred design of World Wide Web user interfaces . 7
6 High-level design decisions and design strategy . 8
7 Content design. 10
8 Navigation and search. 16
9 Content presentation. 26
10 General design aspects . 33
Annex A (informative) Overview of the ISO 9241 series. 36
Annex B (informative) Sample procedure for assessing applicability and conformance . 40
Bibliography . 49

© ISO 2008 – All rights reserved iii

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ISO 9241-151:2008(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 9241-151 was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 4,
Ergonomics of human-system interaction.
ISO 9241 consists of the following parts, under the general title Ergonomic requirements for office work with
visual display terminals (VDTs):
⎯ Part 1: General introduction
⎯ Part 2: Guidance on task requirements
⎯ Part 3: Visual display requirements
⎯ Part 4: Keyboard requirements
⎯ Part 5: Workstation layout and postural requirements
⎯ Part 6: Guidance on the work environment
⎯ Part 7: Requirements for display with reflections
⎯ Part 8: Requirements for displayed colours
⎯ Part 9: Requirements for non-keyboard input devices
⎯ Part 11: Guidance on usability
⎯ Part 12: Presentation of information
⎯ Part 13: User guidance
⎯ Part 14: Menu dialogues
⎯ Part 15: Command dialogues
⎯ Part 16: Direct manipulation dialogues
⎯ Part 17: Form filling dialogues
iv © ISO 2008 – All rights reserved

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ISO 9241-151:2008(E)
Guidance on software individualization is to form the subject of a future part 129.
ISO 9241 also consists of the following parts, under the general title Ergonomics of human-system interaction:
⎯ Part 20: Accessibility guidelines for information/communication technology (ICT) equipment and services
⎯ Part 110: Dialogue principles
⎯ Part 151: Guidance on World Wide Web user interfaces
⎯ Part 171: Guidance on software accessibility
⎯ Part 300: Introduction to electronic visual display requirements
⎯ Part 302: Terminology for electronic visual displays
⎯ Part 303: Requirements for electronic visual displays
⎯ Part 304: User performance test methods
⎯ Part 305: Optical laboratory test methods for electronic visual displays
⎯ Part 306: Field assessment methods for electronic visual displays
⎯ Part 307: Analysis and compliance test methods for electronic visual displays
⎯ Part 308: Surface-conduction electron-emitter displays (SED) [Technical Report]
⎯ Part 309: Organic light-emitting diode (OLED) displays [Technical Report]
⎯ Part 400: Principles and requirements for physical input devices
⎯ Part 410: Design criteria for physical input devices
⎯ Part 920: Guidance on tactile and haptic interactions
Framework for tactile and haptic interaction is to form the subject of a future part 910.
© ISO 2008 – All rights reserved v

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ISO 9241-151:2008(E)
Introduction
It is widely accepted that usability is a key factor in successful website design but until now there has been no
internationally agreed standard that specifically addressed the usability of World Wide Web (WWW or Web)
user interfaces.
World Wide Web user interfaces pose particular usability problems:
⎯ their users are diverse in knowledge, capabilities, language and other factors — for example, a World
Wide Web user interface that works well for subject-matter experts may be sub-optimal for ordinary users;
⎯ users’ goals vary considerably — for example, a site optimized for one set of tasks (such as e-commerce
transactions) could be sub-optimal for users whose tasks are different (such as information gathering);
⎯ different Web browsers or user agents often render Web content in different ways — for example, the
layout of individual pages can change, sometimes quite dramatically.
Users of the World Wide Web will have experienced the problems of inconsistency between websites and
often even within the same website. For example, something as straightforward as a link may be denoted by
underlining on one page, by a mouse-over on a second page and by nothing at all on a third page.
A number of guidelines for good practice exist, many on the Web itself, but these guidelines sometimes
conflict and can also be difficult to put into practice. While not addressing Web user interfaces specifically, a
number of International Standards are available that provide useful guidance on usability and the design of
user interfaces: ISO 9241-11 to ISO 9241-17 and ISO 9241-110 provide ergonomic guidance on the design of
software user interfaces in general, ISO 13407 on achieving usability by incorporating user-centred design
activities throughout the life cycle of interactive computer-based systems, and the ISO 14915 series of
standards on the design of multimedia and hypermedia aspects of user interfaces.
The recommendations and guidelines provided in this part of ISO 9241 apply primarily to the design of the
content of a website or, more generally, a Web application, the user's navigation and interaction, as well as
the presentation of the content. The user interface of different types of user agents (such as Web browsers) or
additional tools such as Web authoring tools are not the subject of this part of ISO 9241, although some
guidelines could apply to those systems as well. Aspects of the technical implementation of the
recommendations are also not within its scope.
An important objective for developing Web user interfaces is to make them accessible to the widest possible
range of users, including persons with disabilities. While some guidance provided in this part of ISO 9241 is
also important for the accessibility of Web user interfaces, it does not aim at covering accessibility in a
comprehensive manner. Common guidance on securing and improving accessibility to ICT (information and
communication technology) equipment, software and services can be found in ISO 9241-20, and detailed
guidance on the accessibility of software user interfaces in general can be found in ISO 9241-171, while the
World Wide Web Consortium's Web Accessibility Initiative provides guidance specifically for Web content,
user agents and authoring tools.
ISO 9241 was originally developed as a seventeen-part International Standard on the ergonomics
requirements for office work with visual display terminals. As part of the standards review process, a major
restructuring of ISO 9241 was agreed to broaden its scope, to incorporate other relevant standards and to
make it more usable. The general title of the revised ISO 9241, “Ergonomics of human-system interaction”,
reflects these changes and aligns the standard with the overall title and scope of Technical Committee
ISO/TC 159, SC 4. The revised multipart standard is structured as series of standards numbered in the
“hundreds”: the 100 series deals with software interfaces, the 200 series with human centred design, the
300 series with visual displays, the 400 series with physical input devices, and so on.
See Annex A for an overview of the entire ISO 9241 series.
vi © ISO 2008 – All rights reserved

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INTERNATIONAL STANDARD ISO 9241-151:2008(E)

Ergonomics of human-system interaction —
Part 151:
Guidance on World Wide Web user interfaces
1 Scope
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 of
Web 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 as Web
authoring tools are not directly addressed in this part of ISO 9241 (although some of its guidance could apply
to these systems as well).
Web user interfaces are presented on a personal computer system, mobile system or some other type of
network-connected device. While the recommendations given in this part of ISO 9241 apply to a wide range of
available front-end technologies, the design of mobile Web interfaces or smart devices could require
additional guidance not within its scope; neither does it provide detailed guidance on technical implementation
nor on issues of aesthetic or artistic design.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 9241-11, Ergonomic requirements for office work with visual display terminals (VDTs) — Part 11:
Guidance on usability
ISO 9241-12:1998, Ergonomic requirements for office work with visual display terminals (VDTs) — Part 12:
Presentation of information
ISO 9241-13, Ergonomic requirements for office work with visual display terminals (VDTs) — Part 13: User
guidance
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ISO 9241-151:2008(E)
ISO 9241-14, Ergonomic requirements for office work with visual display terminals (VDTs) — Part 14: Menu
dialogues
ISO 9241-15, Ergonomic requirements for office work with visual display terminals (VDTs) — Part 15:
Command dialogues
ISO 9241-16, Ergonomic requirements for office work with visual display terminals (VDTs) — Part 16: Direct
manipulation dialogues
ISO 9241-17, Ergonomic requirements for office work with visual display terminals (VDTs) — Part 17: Form
filling dialogues
ISO 9241-20, Ergonomics of human-system interaction — Part 20: Accessibility guidelines for
information/communication technology (ICT) equipment and services
ISO 9241-110, Ergonomics of human-system interaction — Part 110: Dialogue principles
ISO 9241-171, Ergonomics of human-system interaction — Part 171: Guidance on software accessibility
ISO 9241-303, Ergonomics of human-system interaction — Part 303: Requirements for electronic visual
displays
ISO 13407, Human-centred design processes for interactive systems
ISO 14915 (all parts), Software ergonomics for multimedia user interfaces
WCAG 1.0, Web Content Accessibility Guidelines 1.0, W3C Recommendation, World Wide Web Consortium
(W3C) (MIT, INRIA, Keio)
WCAG 2.0, Web Content Accessibility Guidelines 2.0, World Wide Web Consortium (W3C) (MIT, ERCIM,
1)
Keio)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
boolean search
search formulation using logical operators
3.2
browser
user agent allowing a person to retrieve and read hypertext, to view the contents of hypertext nodes (usually
Web pages), to navigate from one node to another, and to interact with the content
NOTE A browser also offers a set of operations, e.g. for navigating websites or for changing the visual appearance of
the content displayed.
3.3
conceptual content model
abstract model describing the concepts of an application domain, the relationships among those concepts and
the operations to be performed on the concepts or relationships

1) Working draft. Intended to supersede WCAG 1.0 in its final published version.
2 © ISO 2008 – All rights reserved

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ISO 9241-151:2008(E)
3.4
content
web content
〈Web user interface〉 set of content objects
3.5
content object
interactive or non-interactive object containing information represented by text, image, video, sound or other
types of media
3.6
dynamic navigation link
computed link
link that is computed dynamically by the system based, for example, on the content of a database
3.7
frame
mechanism for dividing a browser window into independent windows, each displaying a different document, or
different parts of the same document
3.8
frameset
collection of frames and a corresponding layout structure that is presented in the same browser window
3.9
global navigation
set of navigation links available on all pages of a website
3.10
home page
start page
top page
main page through which users typically enter a website and whose URL is typically published or linked as the
main Web address of an organization or an individual
NOTE The term home page can be used differently in different contexts. Some groups will call a complete website a
home page.
3.11
interaction object
component of the Web user interface accepting user input
EXAMPLE Links, buttons, input fields, check boxes or selection lists.
3.12
Internet
worldwide interlinked computer systems and computer networks connected via gateways that enable the
transfer of data between them
3.13
intranet
computer network using Internet standards, the access to which is limited to members of a particular
organization such as a company
3.14
landmark page
landmark
main page in the navigation structure that can be directly accessed from many other pages
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ISO 9241-151:2008(E)
3.15
link
hyperlink
〈World Wide Web〉 reference from some part of one document to (some part of) another document or another
part of the same document
NOTE Links are also called hyperlinks because hypertext and hypermedia systems make extensive use of this
concept. Links are used for activating navigation. They are represented, for instance, as element tags in the hypertext
markup language (HTML). The concept of links is also described in ISO 14915-2 in the context of multimedia user
interfaces.
3.16
link cue
textual or graphical presentation of a link showing information about the link target
3.17
media object
component of a Web document that is implemented by a single media type
EXAMPLE 1 A text object presenting a discussion about some topic.
EXAMPLE 2 An image object presenting a picture of some person.
EXAMPLE 3 A sound object presenting a song.
NOTE Adapted from ISO 14915-2:2003, definition 3.3.
3.18
navigation component
group of navigation elements placed together
3.19
profile
user profile
set of attributes used by the system that are unique to a specific user/user group
3.20
predefined user profile
profile based on a stereotype or combination of stereotypes
NOTE 1 Stereotypes used as the basis of a predefined user profile could include a role, a job function or a group
membership.
NOTE 2 Predefined user profiles are often used to define access privileges to specific Web content.
3.21
rendering
act whereby the information in a document is presented
NOTE This presentation is done in the form most appropriate to the environment (e.g. aurally, visually, in print).
3.22
navigation
Web navigation
〈World Wide Web〉 movement between or within Web pages or the movement within some presentation
segment presented on a page (e.g. the movement within a particular media object) that users perform to find a
specific function or piece of information
NOTE 1 In this part of ISO 9241, navigation is used as a convenient short form for Web navigation (see also
ISO 14915-2).
NOTE 2 Navigation steps are often initiated by activating some link.
4 © ISO 2008 – All rights reserved

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ISO 9241-151:2008(E)
3.23
navigation structure
Web navigation structure
〈World Wide Web〉 structure composed of elementary or composite presentation segments (such as Web
pages or media objects contained in a page) and links, determining all possible paths on which users can
move around in a Web user interface
3.24
screen reader
assistive technology that allows users to operate software without needing to view the visual display
NOTE 1 Output of screen readers is typically text-to-speech or Braille.
NOTE 2 Screen readers rely on the availability of information from the operating system and applications.
3.25
site map
textual or graphical overview of the complete navigation structure of a website
3.26
splash screen
temporary page shown prior to the homepage when a website is first accessed
3.27
tool tip
small pop-up window that appears when the mouse pointer is moved over an interaction object and that
shows explanatory text or help information
3.28
transaction
action that involves inserting, updating or deleting information
3.29
Web user agent
user agent
front-end software that enables users to interact with a remote system through Internet protocols
NOTE A browser is a specific type of user agent.
3.30
uniform resource locator
URL
mechanism for identifying resources on the Internet (such as Web pages) by specifying the address of the
resource and the access protocol used
NOTE The official technical term as specified by the IETF is uniform resource identifier (URI), of which URL is a
subset.
3.31
Web page
coherent presentation of a content object or set of content objects and associated interaction objects through
a user agent
3.32
Web service
Web resource providing content and/or functionality that can be accessed remotely through standardized
protocols and software interfaces
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ISO 9241-151:2008(E)
3.33
website
site
coherent collection of interlinked Web resources (for example, Web pages or Web services) that is located on
one or several computers connected to the Internet, and that can usually be accessed through the same
domain specification part of a URL
3.34
Web application
World Wide Web application
application providing functionality to the user through a browser or other type of user agent using Web formats
and protocols
NOTE Web applications in the sense of this part of ISO 9241 comprise websites that only deliver content, that
combine content delivery with application-specific functionality or that provide only specific application functionality such as
a particular Web service.
3.35
Web user interface
World Wide Web user interface
all aspects of a website or Web application related to content, functionality, navigation, interaction and
presentation that are relevant for using a website or Web application
3.36
within-page link
link leading to a target on the same page
4 Application
4.1 Intended user groups
The following groups are intended users of this part of ISO 9241:
⎯ developers and designers of Web user interfaces who will apply it during the development process;
⎯ content providers who generate and maintain the content of a website or application;
⎯ developers of content authoring tools who will integrate the mentioned recommendations into their
authoring tools;
⎯ usability evaluators who will check that Web user interfaces meet its recommendations;
⎯ buyers who wish to ensure the ergonomic quality of a software product or development.
4.2 Applying the recommendations
Each individual recommendation in this part of ISO 9241should be evaluated for its applicability and, if judged
to be applicable, should be implemented, unless there is evidence that to do so would cause deviation from
the design objectives or would result in an overall degradation in usability. In some cases, the designer may
need to trade off one principle or recommendation in favour of another to achieve an optimal design.
4.3 Conformance
If a claim of product or application conformity with this part of ISO 9241 is made, the procedure used in
establishing requirements for developing and/or evaluating World Wide Web user interfaces shall be specified.
The level of specification of the procedure is a matter of negotiation between the involved parties. Annex B
provides a basis both for determining and recording the applicability of all the recommendations and a means
for reporting that they have been
...