Mobile Web Best Practices 1.0

W3C Working Draft 17 October 2005

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Charles McCathieNevile, Opera Software
Jo Rabin, mTLD Mobile Top Level Domain (.mobi)


This document specifies best practices for Web content when accessed from mobile devices.

It is directed at all participants in the mobile value chain.

The primary goal is to improve the user experience of the Web when accessed from mobile devices.

Status of this Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

This document describes the best practices for content to work well on mobile devices. A companion scope document [Scope] describes the scope of this work.

This is the first Public Working Draft for review by interested parties. Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

This draft does not represent the consensus of the MWBP Working Group. It is known to be missing requirements, and is likely to contain errors.

This document has been produced by the Mobile Web Best Practices Working Group as part of the Mobile Web Initiative. There are several specific issues on which the group solicits public feedback and comment. They are called out in the text like this note. We encourage feedback on all aspects of the document but particularly request feedback on these points. Please send comments on this document to the working group's public email list public-bpwg@w3.org, a publicly archived mailing list..

This document was produced under the 5 February 2004 W3C Patent Policy. The Working Group maintains a public list of patent disclosures made in connection with this document; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) with respect to this specification must disclose the information in accordance with section 6 of the W3C Patent Policy.

Table of Contents

1 Introduction
    1.1 Purpose of the Document
    1.2 Audience
        1.2.1 Players in the Mobile Value Chain
    1.3 Scope
        1.3.1 Phasing
        1.3.2 Usability
        1.3.3 Boundaries of the Best Practice Guidelines
    1.4 Baseline Client
    1.5 Compliance
    1.6 Relationship to other best practices and recommendations
2 How the Best Practices are Organized
3 Requirements
    3.1 User Experience
    3.2 Input
    3.3 Bandwidth and Cost
    3.4 Content Type
    3.5 Advertising
    3.6 Device Limitations
    3.7 Advantages
4 Delivery Model Architecture
    4.1 Adaptation Implementation Model
    4.2 Assumptions about Adaptation
5 Best Practices
    5.1 Overview
        5.1.1 Sources
        5.1.2 How this section is organized
        5.1.3 Structure of Best Practice Statements
    5.2 Overall Behavior
        5.2.1 Establish the Context of the Device
        5.2.2 Exploit Client Capabilities
        5.2.3 Work around deficient implementations
        5.2.4 Error Messages
        5.2.5 User Preferences
        5.2.6 Testing
        5.2.7 [Other general things]
    5.3 Navigation and Links
        5.3.1 URLs of Site Entry Points
        5.3.2 Provide a Site Map
        5.3.3 Balanced Structure
        5.3.4 Thematic Consistency of Resource Identified by a URI
        5.3.5 Navigation Mechanisms
        5.3.6 Access Keys
        5.3.7 Link Target Identification
        5.3.8 Image Maps
        5.3.9 Refreshing, Redirection and Spawned Windows
    5.4 Page Layout and Content
        5.4.1 Page Content
        5.4.2 Consistency
        5.4.3 Page Size
        5.4.4 Scrolling
        5.4.5 Navigation Bars etc. [Extraneous material]
        5.4.6 Graphics
        5.4.7 Color
        5.4.8 Background Images
    5.5 Page Definition
        5.5.1 Title
        5.5.2 Frames
        5.5.3 Structural Elements
        5.5.4 Tables
        5.5.5 Non Text Items
        5.5.6 Valid Markup
        5.5.7 Measures
        5.5.8 Semantic Markup
        5.5.9 Style Sheets
        5.5.10 Minimize
        5.5.11 Content Types
        5.5.12 Character Set
    5.6 User Input
        5.6.1 Input
        5.6.2 Tab Order
        5.6.3 Labels
        5.6.4 Language Identification
        5.6.5 Context Menus
6 Techniques
7 Conformance and mobileOK


A Glossary (Non-Normative)
B Acknowledgements (Non-Normative)
C References (Non-Normative)

1 Introduction

1.3 Scope

The scope of these Best Practices is laid out in [Scope]. In summary this document refers primarily to browsing and extension of the Web browsing experience to be more usable on mobile devices.

The charter of the group is to specify best practices for delivery to mobile devices. Hence best practice statements that do not specifically have a mobile aspect are not included. In particular many Web Content Accessibility [WCAG] guidelines are general to all forms of Web access and are not repeated here unless they have a specific mobile interpretation.

1.3.1 Phasing

As discussed in [Scope] the are many aspects to Mobile Web Best Practices.

One of those aspects is that, at present, the design and construction of many Web sites and pages make for a poor user experience when those sites and pages are viewed on a mobile device.

While improving those Web sites is only one aspect of improving the user experience, significant improvements can be achieved in this way, hence the first phase of work is concerned with providing guidelines for Web-site and content developers.

In future phases other aspects may be considered - e.g. best practices as applied to adaptation and devices. Also in future phases the scope of the recommendations may be extended beyond 'Traditional Web Browsing' into fields such as voice browsing.

1.3.3 Boundaries of the Best Practice Guidelines

This section describes what the Best Practices are trying to achieve, and what they are not. A Reasonable User Experience

The MWI in this phase [See Phasing] is concerned with establishing a set of guidelines that help content providers achieve the best possible experience of their Web content - given the client and network limitations that are encountered in the mobile delivery of Web content [see Requirements for a discussion of these]. A reasonable experience of the Web cannot be achieved on clients that exhibit too many of the limitations discussed or where one or other of the limitations is very severe.

In saying this it is recognized that any judgment of what is a reasonable experience is made at a particular point in time and from particular cultural perspective. It is also recognized that it is possible to achieve a reasonable experience of non-Web services in the presence of such limitations and that that there are at present many such services, often implemented using WAP 1.x technologies. The intention, however, of the Mobile Web Initiative, is to extend the reach of the Web to mobile devices. Hence such non Web services are out of scope of this discussion. Which Formats are in Scope?

Similarly to the [WCAG] the best practice recommendations are couched at a level of generality that allows them to be applied to a wide range of markup languages. The intention being that as well as being applicable to current Web standards (especially XHTML), they are also applicable to existing and legacy non-Web recommendations, such as cHTML and WML, as well as future standards, such as [CDFWG].

1.4 Baseline Client

The group requests public comment on the specification of the baseline device given the comments in the previous section, that the purpose of the baseline specification is to inform what implementations can assume to be the minimum level of support that they must take account of, and what assumptions they may make in the absence of any other information.

In addition to discussing the baseline client the group has also discussed the idea of a default client. The idea being that for any particular application or geographic region, it may be known that the majority of devices are of a particular type or support particular features. In this case the notion of the 'global' baseline device is supplemented by a 'local' default device, which may have either greater or lesser functionality when compared with the baseline.

The group would value feedback both on which parameters are to be specified and what the values for those parameters should be.

The following are for illustration only.


For the purposes of delivering The Web, this is assumed to be a version of XHTML - probably aligned with XHTML-MP. Some opinion states that WML should be assumed. http delivery is assumed.

There is a further variation in views as to what image format a web site should assume a client supports. It may be that it should be assumed that there is no compatible image support.

Usable Screen Size

People have strong, but divergent opinions on this. The absolute minimum being 96 x 96 pixels. Strong support is expressed for 128 x 128, however a vocal group supports bigger still.

Some opinions support the notion that a minimum row and column availability for text presentation needs to be specified.


Varying opinions again on this.

Maximum Page Weight

It is important to understand the limitations of memory so that Web sites do not try to deliver pages that are too big. However it is not clear how this should take into account the combined weight of markup and images. Suggestions vary from 10k bytes upwards.


Many other candidate parameters have been suggested, including cpu power, Back / Forward navigation in history, text entry (which character sets?), form controls, SSL 1/2, Javascript ...

1.6 Relationship to other best practices and recommendations

These recommendations are in part derived from the Web Content Accessibility Guidelines [WCAG]. As noted above, WCAG guidelines are supplementary to the Mobile Best Practices, whose scope is limited to matters that have a specific mobile relevance.

The work of the Device Independence Working Group [DIWG] has a direct and fundamental relevance to this document.

2 How the Best Practices are Organized

The document is organized as follows:


Describes the audience, purpose and scope of the document.


This section, explains the format of the document.


An illustration of the type of problems that the Best Practices are intended to ameliorate.


Discusses the environment within which the mobile web is realized, with particular reference to adaptation.

Best Practices

The statements themselves


How to implement the best practices [not present in this draft].

Conformance and mobileOK

Testing for conformance to and labeling with the trust mark [not present in this draft].


Glossary [not present in this draft]



3 Requirements

This section discusses the requirements of the Mobile Web Best Practice statements in section 5. The statement of requirements is intended to be illustrative rather than exhaustive or complete.

We discuss the requirements under two broad headings, User Experience and Device Limitations; both contribute to a poor experience of the Web on mobile devices.

4 Delivery Model Architecture

The widely varying characteristics of mobile devices can make it difficult for a Web site to provide an acceptable user experience across a significant range of clients. For example different clients support different markup features, and the different screen sizes may demand different sized images.

Consequently, it is very common when delivering content to mobile clients to vary the details of the markup, format of images, image sizes, color depths and so on, to suit the characteristics of the client in question. The process of altering content in this way to enhance the user experience on particular devices is referred to as content adaptation.

The remainder of this section outlines content adaptation in order to provide a background to this document. It is not intended as a comprehensive guide or to be definitive. The Device Independence Working Group [DIWG] has published a great deal of material relevant to this subject. Readers are expecially referred to "Delivery Context Overview for Device Independence" [DCODI].

In addition, the sister group of the Best Practices Working group - the Device Descriptions Working Group, is currently defining requirements for a repository of mobile client characteristics that are relevant to content adaptation.

4.2 Assumptions about Adaptation

In phase 1 we assume that content adaptation, if any, is carried out Server Side. Future phases may consider the implication of other content adaptation, especially the issues around granting authority to third parties to carry out adaptation, prohibiting adaptation and so on. Later phases may also address the issues around the possibility of multiple adaptations - i.e. the possibility that adaptation can be applied in more than one place, and that in network adaptation may occur more than once.

We also assume that it is possible to create a site that is consistent with the best practice recommendations, without carrying out adaptation at all. However, it is likely that a more sophisticated and enhanced user experience will be achieved if adaptation is used.

Clearly in order to determine the appropriate adaptation for any particular access, it is necessary to determine the device that is accessing the service. Sometimes it is not possible to determine the device type, either because the device does not present this information to the server at all, or in sufficient detail, or because the server does not provide the ability to inspect and act on the information provided.

In these cases the content author is expected to assume baseline or default device characteristics, as discussed in the Introduction to this document.

The group seeks public feedback on the desirability of stating that, in practice, adaptation is required for delivery to mobile devices; and that consequently, in view of the desirability of making content widely accessible across a broad range of devices, all Web development requires adaptation.

5 Best Practices

5.1 Overview

5.1.1 Sources

The best practice statements have been assembled by the BPWG from a number of sources. Primary among those are:

5.2 Overall Behavior

There are some general principles that underlie delivery to mobile devices.

In this section we refer to 'Implementations' by which we mean Web Servers, Adaptation Devices and other components in the delivery chain (as discussed above under 'Delivery Model Architecture').

5.2.1 Establish the Context of the Device

Implementations should take all reasonable steps to find out about the device/browser (client) capabilities, adaptation and other transformation that takes place for any instance of an access to a resource.

5.2.4 Error Messages

Provide informative error messages, and a means of navigating away from an error message back to useful information.

5.3 Navigation and Links

Because of the limitations in display and of input mechanisms, the possible absence of a pointing device and other constraints of mobile clients, care should be exercised in defining the structure of a site and the navigation model for the site.

5.4 Page Layout and Content

5.5 Page Definition

5.5.5 Non Text Items

Provide textual alternatives for non-text elements

Do not embed objects or script in pages unless you know the device supports them

When an appropriate markup language exists use markup rather than images to convey information if the device supports it.

Always specify the size of images in markup

When resizing images do so at the server

5.6 User Input

This section contains statements relating to user input. User input is typically more or a lot more restrictive on Mobile devices, which may lack pointing devices and usually do not have a standard keyboard with which to enter text.

6 Techniques

[to be done after best practices agreed]

7 Conformance and mobileOK

[to be done]

A Glossary (Non-Normative)

[to be done]

[Definition: HTML Hypertext Markup Language]

B Acknowledgements (Non-Normative)

The editors would like to thank the members of the Best Practices Working Group for their contributions to the document.

The editors apologize if anyone's name has accidentally been left off the list and invite people to remind us by mail so this can be corrected in future drafts.

C References (Non-Normative)

"Scope of Mobile Web Best Practices ", Phil Archer, Ed Mitukiewicz, W3C Working Draft 1 September 2005 (See http://www.w3.org/TR/mobile-bp-scope/.)
"Web Content Accessibility Guidelines 1.0", W Chisholm, I. Jacobs, G Vanderheiden eds. W3C Recommendation 5 May 1999. (See http://www.w3.org/TR/1999/WAI-WEBCONTENT-19990505.)
DI WG References (See http://www.w3.org/2001/di/Group/.)
Delivery Context Overview for Device Independence (See http://www.w3.org/TR/di-dco/.)
CDF WG References (See http://www.w3.org/2004/CDF/Group/.)
iMode (See http://www.iMode.nl/pdf/download/How_to_create_an_i-mode_site_1_3.pdf.)
Opera's Making Small Devices Look Great (See http://my.opera.com/community/dev/device/.)
Openwave (See http://developer.openwave.com/dvl/support/documentation/guides_and_references/best_practices_in_xhtml_design/index.htm.)
Nokia Guidelines for XHTML-MP on Series 60 (See http://sw.nokia.com/id/4f7b6805-47d7-4914-885c-6ef2b487adf6/Series_60_Platform_Designing_XHTML_MP_Content_v1_4_en.pdf.)
Bowsing on Mobile Phones, paper by Virpi Roto, Nokia (See http://www.research.att.com/~rjana/WF12_Paper1.pdf.)
Little Spring Design (See http://www.littlespringsdesign.com/design/styleguides.html.)