Accessibility

Explanation Checklist

Explanation

It is important that all people who want to view your website are able to do so. The users of your website might have physical limitations or they might be using hardware and software platforms with limited capabilities. You will want to accommodate the users with these limitations by removing any barriers that might make viewing your websites difficult. Reducing the barriers to accessibility can be accomplished by understanding and applying these rules to your websites.

 

Disclaimer: The following items provide links to other sources of web usability information. By selecting these links, you will be leaving NIST webspace. We have provided these links to other websites because they might have information that would be of interest to you. No inferences should be drawn on account of other sites being referenced, or not, from this page. There might be other websites that are more appropriate for your purpose. NIST does not necessarily endorse the views expressed, or concur with the facts presented on these sites. Further, NIST does not endorse any commercial products that are mentioned on these sites.

 

Limitation Issues
Screen reader access

A visually impaired person using a screen reader is hindered if graphics, sounds, colors, animations and video clips have no text equivalent.

Links that are not descriptively named are not useful when using a screen reader.

See Mike Paciello's paper,
People with Disabilities Can't Access the Web!".
Eric Bergman (SunSoft) and Gregg Vanderheiden (Trace R and D Center, University of Wisconsin) discuss disabilities and the use of "assistive technologies" in their document, "Design of HTML Pages to Increase their Accessibility to Users with Disabilities Strategies for Today and Tomorrow".

Internet Browsers

Frames might cause undesirable results.

See Adrian Roselli's list of issues that frames raise, "Some Caveats with Using Frames".

Colors might be treated differently.

Linda Weinman discusses the use of color in her article, "The Browser Safe Color Palette".

Browser specific features should be avoided for public websites.

Jahn Rentmeister's article, "This page optimized for ..." explains why using browser specific features is not recommended.

Internet connection speeds

Time to load pages with large amounts of graphics might be intolerable.

Times to download software might be excessive.

Thomas Mace's article, "On the Web, less is more...." outlines the tools needed to optimize download times.

Jakob Nielsen provides insights into internet bandwidth issues in his article, "Nielsen's Law of Internet Bandwidth".

See Jakob Nielsen's report on "Sun's New Web Design", especially his comments on speed issues.

Hardware platforms

All visitors to the website might not have audio and video capabilities on their computers.

Jakob Nielsen's article, "Guidelines for Multimedia on the Web" presents sound advice for the use of multimedia on web pages.

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Checklist for Accessibility

Disclaimer: The following items provide links to other sources of web usability information. By selecting these links, you will be leaving NIST webspace. We have provided these links to other websites because they might have information that would be of interest to you. No inferences should be drawn on account of other sites being referenced, or not, from this page. There might be other websites that are more appropriate for your purpose. NIST does not necessarily endorse the views expressed, or concur with the facts presented on these sites. Further, NIST does not endorse any commercial products that are mentioned on these sites.

The following table contains the checks performed by WebSAT along with the problems that might be caused by failure to provide the indicated html. For more information: see accessibility guidelines.

 

Html check

Potential problem

Rule:

Include text equivalent via the alt tag for images that are not links.

WebSAT returns:

# of images not used as links and do not have any associated ALT tag text.

WebSAT flags all images that do not contain text equivalent via the alt tag. This rule is meant to alert the web site designer to the importance and purpose of using text equivalent via the alt tag when using images. When a user cannot see a visual image, the inclusion of text equivalent via the alt tag is helpful as it allows the user to understand the purpose of the visual components of the page. There are a number of reasons users might be unable to see visual components: the browser does not support this feature, the user chooses not to view them, or the user has a visual impairment (blindness or low vision). For the visually impaired, screen readers and other assistive technologies are used to read the contents of web pages. If an image exists on your web page, but there is no text equivalent via the alt tag associated with that image, it will be difficult for the user to grasp a sense of the purpose of the image. The use of text equivalent via the alt tag for images requires the designer's judgment since the way in which screen readers perform these tasks is varied. To find out more about text equivalent via the alt tag, visit: W3C Web Accessibility Initiative (WAI).

Rule:

Include text equivalent via the alt tags for images that are links.

WebSAT returns:

# of images used as links and do not have any associated ALT tag text.

WebSAT flags all images used as links that do not contain text equivalent via the alt tag. This rule is meant to alert the web site designer to the importance and purpose of using text equivalent via the alt tag when using images as links. When a user cannot see a visual image, the inclusion of text equivalent via the alt tag is helpful as it allows the user to understand the purpose of the visual components of the page. There are a number of reasons users might be unable to see visual components: the browser does not support this feature, the user chooses not to view them, or the user has a visual impairment (blindness or low vision). For the visually impaired, screen readers or other assistive technologies are used to read the contents of web pages. If an image exists on your web page as a link, but there is no text equivalent via the alt tag associated with that image, it will be difficult for the user to grasp a sense of the purpose of the image. The use of text equivalent via the alt tag for images as links requires the designer's judgment since the way in which screen readers perform these tasks is varied. To find out more about text equivalent via the alt tag, visit: W3C Web Accessibility Initiative (WAI).

Rule:

Include text equivalent via the alt tag when using java applets.

WebSAT returns:

# of java applets that do not have associated ALT tag text.

WebSAT flags all java applets that do not contain text equivalent via the alt tag. This rule is meant to alert the web site designer to the importance and purpose of using text equivalent via the alt tag when using java applets. Including text equivalent via the alt tag is helpful for users who cannot see visual images on a page. Text equivalent via the alt tag allows the user to understand the purpose of the visual components of the page, even though they cannot see the image. There are a number of reasons users might be unable to see visual components: the browser does not support this feature, the user chooses not to view them, or the user has a visual impairment (blindness or low vision). To find out more about text equivalent via the alt tag as it relates to applets, visit: W3C Web Accessibility Initiative (WAI).

Rule:

Include text equivalent via the alt tag or links for image maps.

WebSAT returns:

# of image maps that do not have associated ALT tag text.

WebSAT flags image maps that do not contain text equivalent via the alt tag or links. Text equivalent via the alt tag can be read by screen readers and tell a visually impaired user that there is a link that can be followed. To find out more about text equivalent via the alt tag or links for image maps, see: W3C Web Accessibility Initiative (WAI).

Rule:

Include the NOFRAMES option when using frames.

WebSAT returns:

A "NO" if frames are used in a specified frameset without an associated NOFRAMES usage.

WebSAT flags frames when the "noframes" option is not used. The "noframes" option allows the web page designer to provide alternate text for users who have browsers that do not display frames. Developing frames by using html code is complex and requires that the developer understand the use of the frame tags. For more details on using frames, see Dan Bricklin's article: "When (and how) to use frames".

Rule:

When specifying colors, use the RGB hexidecimal values. This helps to insure proper color recognition by any browser which does not recognized specified "color names".

WebSAT returns:

WebSAT returns the number of color specifications which were not assigned as RGB hexidecimal values.

RGB colors form the common subset that can be predictably displayed on all hardware platforms. Visit "Hexadecimal Color Chart: Specifying Colors on the Web".

Rule:

Combine the use of BG color and TEXT color attributes. Do not use them alone.

WebSAT returns:

A "NO" if the BG and TEXT color attributes are not used in combination.

If you are setting background colors and not text colors, or vice versa, you could create an unreadable page due to the default colors of some browsers. See "The L-Space Web" for tips on background colors.

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Version 2.2
Page last modified: 15 May 2002
National Institute of Standards and Technology (NIST)