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Marty Carroll, Director of Usability Practice, The Usability Company
Below is a list of key issues and considerations for usability and accessibility that are applicable to all websites.
Images and Animations:
Accessibility: Alt tags - the descriptive text attached to graphics, which allows screen-readers to articulate them - should accompany every image, even blank spaces comprised by gifs. Animations should be kept to a minimum and should include an option to switch them off
Usability: Alt tags help those without sight problems because they provide useful information about the images that may not be clear from their appearance. In addition, for those on slower Internet connections, alt tags provide information on downloading images allowing the user to decide whether they want to wait for the download or not
Image Maps:
Accessibility: If an image is a link then it should have alt tags, which say what the image links to
Usability: It does not suffice to simply have a description of the image in the alt tag if the image is a link. The alt tag should always provide information on where it is linking to in the same way as a text link
Multimedia:
Accessibility: A website should provide captioning and transcripts of audio material and descriptions of video
Usability: While much has been made of multimedia, many Internet users in the UK do not have the bandwidth to support multimedia. Alternative presentation of multimedia (such as text) should always be provided to accommodate these users and for those whose environment (busy office, quiet train coach, etc) precludes their use of multimedia
Hypertext Links:
Accessibility: Use text that makes sense when read out of context. For example, avoid repetitive use of "click here" and "more"
Usability: Use words that describe the feature or the function of the destination page because this allows users to make informed decisions on whether they wish to use the links. Research shows that people often scan a page for links rather than reading all of the text available so descriptive links are paramount
Page Organization:
Accessibility: Where possible, use style sheets to keep content data separate from the data governing that content's presentation
Usability: Style sheets allow for consistency in the presentation of information and consistency is the hallmark of usability. Good use of style sheets mean that people learn to use sites effectively much more quickly
Graphs and Charts: Accessibility: Use 'Longdesc tags' with graphs and charts because these tags provide in-depth textual descriptions of contents
Usability: The provision of 'Longdesc tags' can help with communicating the meaning of complicated graphs and charts. Using 'Longdesc tags' to convey this information can save valuable screen space
Scripts, Applets, and Plug-ins:
Accessibility: Provide alternative content in case active features are inaccessible or unsupported
Usability: The security setting on a user's PC or the presence of a company firewall often means that features may be unavailable to a large part of the population. Many of the new Internet users feel intimidated using the Internet and will not install plug-ins on their PC's
Frames:
Accessibility: Provide a "no frames" option and if frames are used; make sure the titles attached to them are meaningful
Usability: The use of frames means that it is difficult to bookmark pages of a site. If someone wants to send a web address to a friend via email for reference purposes then copying the URL from the browser will not work if frames are used because the URL refers to the frameset rather than the page the user is viewing
Tables:
Accessibility: Rows and columns need to relate to one another so that information in each cell can be understood in context
Usability: N/A
Check your work:
Accessibility: Look out for simple spelling mistakes and check that the accessibility elements added meet W3C's guidelines at http://www.w3.org/TR/WCAG
Usability: Of course, the presence of simple spelling mistakes conveys the impression that the site is shoddy and will consequently lead to a lack of trust. Conformance to accessibility guidelines does not necessarily equate to good accessibility - how people with various disabilities actually use the site needs to be taken into account. For example, while software may indicate that alt tags are present these alt tags may not be very useful
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