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Web Accessibility Best Practices from NASA Webmaster Community (Internal weblink)

How to perform a site assessment:

• Use Bobby http://www.cast.org/bobby to perform a page-by-page assessment.
• Create a site listing, by level, with specific URLs for each page at each level.
• Use the site listing of URLs as a "feed" list of URLs for Bobby. Bobby only reviews the contents of the specific URL which is entered.
• Run all the URLs through Bobby.
• Bobby produces a listing of the HTML contents of the page and reports on whether or not the use of that HTML code (as it "sees" it) is appropriate for accessibility.
• The Bobby report becomes the page guideline for reviewing or fixing a particular page. Review all Bobby reports and note the "Priority 1" comments.
• The General Services Administration's Center for Information Technology Accommodation (CITA), runs a one-stop URL checking page at http://w3.gsa.gov/web/m/cita.nsf. This service allows you to enter the URL of a page to check and the server-side software will return direct links to Bobby, a Lynx-like viewer, the WAVE tag checker, a W3C HTML 4.x compliance checker, and several other accessibility test tools.

Easy, First Steps in Making a Webpage or Website Accessible:

• Most of us have known all along that we should use the ALT tag to provide information about JPG and GIF files. Go back and add ALT tags to EVERY image and TITLE or NAME for all HREF tags, and where it will provide value, ALT or SUMMARY or HEADERS for every TABLE, TD and TR tag.
• Using the ALT tag will get most sites up to at least a minimal accessibility level.
• One quick way to determine the extent of ALT tag renovation is to use GREP or "Find File" (depending on your operating system) and search on either the extension (.JPG/.JPEG or .GIF) or the type (IMAGE). Do the search for the entire set of directories/folders which comprise the site's hierarchy. A count and/or listing of the instances GREP or "Find File" returns also becomes your checklist for the site.
• An important additional cautionary measure is to include all media types in your search. This would include .QT, .MOV, .AVI, .MPG/.MPEG, .WAV, .AIFF, .SND, .SWF, .RM, .RA, .RAM, .SMIL, etc.
• As procedures for encoding Real, Media Player, and Quicktime files with equivalent data become known, they will be posted here.
• The use of FRAMEs included the NO FRAME tag. Most FRAME sites do have NO FRAME information. If your page or site uses FRAMEs and you haven't included NO FRAMEs tags, go back and add them. For sites which already have NO FRAME (and for those creating new) tags, make sure that the content of the NO FRAME portion is both meaningful and readable. Run you page through a Lynx viewer or use GSAs one-stop URL checker to have a Lynx-like read-back from your page.
• If you use TABLEs for page layout, you have several choices.
• The preferred method of defining page layout in the HTML 4.x specification is to use Style Sheets.
• The consensus among NASA webmasters is there are insufficient numbers of browsers in use which support the CSS specifications correctly, converting from TABLE or FRAME to Style Sheets is sufficiently labor-intensive, the use of TABLE for layout will continue for some time. (See below for discussion of issues associated with website layout.)
• If you can't convert to a non-TABLE layout or chose not to use Style Sheets then provide a SUMMARY tag for the TABLEs used for layout which describes the layout function. Normally, SUMMARY would be used to summarize the purpose of a data table.

Use a Checklist to Assess, Validate or Verify

• The checklist provided is only a tool.  Use it to assess a site; use it to verify a site has been repaired; use it to provide validation that a site is, indeed, accessible.

Practical Approach to Assessing and Repairing Entire Sites

Rate sites in two stages.

• Stage 1 would be the easier guidelines to comply with, and;
• Stage 2 would be the more difficult ones.

Suggested list for Stage 1:

1. ALT tags for images that are clear and informative;
2. Use color as a subordinate element in conveying online information and navigation;
3. Use the language identification tag in the head area of HTML documents;
4. Convert server-side image maps to client-side image maps;
5. Identify row and column headers on data tables (one interpretation of this guideline is that tables used for layout would not require this);
6. Frame titling and "no frames" equivalent text;
7. Improve content tracking as best as can done - this area includes a group of recommendations such as using consistent navigation, separating links clearly, providing jump links around link lists, etc.

Suggested list for Stage 2:

1. Provide static pages that are regularly updated for sites that rely on dynamic delivery of information;
2. Provide equivalent alternatives for multimedia products (closed captioning);
3. When using Style sheets make sure the site works if the browser doesn't support Style Sheets.

Potential Metric Elements:

1. Look at the proposed guidelines;
2. Figure out what it would take to comply by the deadline if all possible resources were applied;
3. Once you can quantify what it would take, you are in a position to propose what you can realistically do.

The World Wide Web Consortia Web Accessibility Guidelines recommend Style Sheets over Frames and recommend against using Tables.

The current versions of several popular Reader Software packages handle Frames quite nicely and are nearly as good at handling Tables. This is even more true when the appropriate alternate, summary and heading tags are provided.

Only one of the many current browsers (Microsoft Internet Explorer, PC/Mac) comes close to providing compliance with the current Cascading Style Sheet (CSS) specification (CSS2, also see the specification for CSS1).

This presents the following truths:

One approach Headquarters is taking is to identify the best use of which tags will allow Tables to continue to be used as a layout tool. This is being done by first using the Bobby software and then using individuals who rely on Reader Software to access the web and determining if the site passes Bobby or not and whether the individuals using Reader Software perceive the content as it is intended. This is an iterative process and we are not yet at a point where we can report a trend or provide recommendations.

Given the ease with which Frame pages can be accessed and the content perceived accurately by those using Reader Software, previous constraints might be reexamined on the use of Frames for sites which get heavy use by recent version browsers. Such sites would probably also be fairly simple Tables, too, though. Each approach appears to have some advantages and some disadvantages.

Useful links relevant to site usability and accessibility

Useful links relevant to current site design, including JavaScript & DHTML

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Author Charles Redmond NASA Headquarters

Curator Charles Redmond

This document last updated January 21, 2001.