Accessibility Guidelines Implementation

This applies to Page Valet, and the online Accessibility Valet. AccessValet Level 2 reports overcome the limitations described here by interactive checking, but are only available in commercial versions of the tool.

Starting at Version 3.1, Page Valet supports accessibility checking, in addition to the markup normalisation and validation already performed.

Whereas validation tells you with certainty whether a document complies to a standard, checking against accessibility guidelines is more heuristic, and cannot be fully automated in a tool such as Page Valet. In general, the best an automated check can do is to identify potential problems, and draw them to your attention.

Design Considerations

Level of Testing

Page Valet's accessibility checks apply to elements and attributes. Accessibility warnings are tied to the element that gives rise to the warning, making the problem immediately obvious from the report. The downside of this is that a warning may recur frequently, leading to long reports.

Checks and Guidelines

Whilst the checks are based closely on the guidelines, and will always reference a particular guideline in the event of failure, there is no direct correspondence between guidelines and checks. Many checks deal with more than one guideline, while some guidelines require more than one check.

Dealing with Uncertainty

Some problems can be identified with a high degree of certainty: for example, use of the <font> element is a violation of a guideline to use CSS for layout and presentation. Others are less certain: for example, the <script> element can cause major problems, but correctly used it is harmless, and may indeed improve accessibility. Some of the WCAG guidelines concerning scripting are correspondingly vague. Page Valet deals with this by assigning confidence levels to its accessibility warnings. A confidence level of certain implies there is definitely a violation, while high, medium and low imply progressively less certainty, with low meaning something that is probably fine but should be noted for completeness.

Dealing with Information Overload

Page Valet reports on elements and attributes of your markup. There are some accessibility guidelines that apply throughout a document, and should in principle be reiterated throughout a document. For example, a guideline to use clear language, or one to identify changes in a document's natural language, can apply to any element that contains text, yet applying meaningful tests for these guidelines is beyond the scope of Page Valet. Highlighting huge numbers of possible violations will tend to overburden the user with reports, the overwhelming majority of which are irrelevant. Page Valet deals with this by omitting reports where no meaningful test can be applied.

Reference

US Government Section 508 Guidelines

Every clause in the Section 508 guidelines is explicitly tested. Where a possible violation is detected, a warning is displayed.

Web Content Accessibility Guidelines (WCAG)

Page Valet WCAG Compliance Reference
PriorityCheckpointTestedComments
 
11.1YesSeveral tests for aspects of this, not just the usual test for ALT attributes.
11.2ImpliedDealt with under #9.1
11.3YesPassive test
11.4YesPassive test
31.5YesPassive test
 
12.1Yes 
32.2No 
 
23.1No 
23.2YesValidation is rigorous and formally correct
23.3Yes 
23.4No 
23.5Yes 
23.6ImpliedViolations will be shown as validation errors
23.7Yes 
 
14.1NoWe cannot detect changes in language
34.2Yes 
34.3Yes 
 
15.1Yes 
15.2YesTest is limited
25.3ImpliedViolations will generate warnings from other tests
25.4No 
35.5Yes 
35.6Yes 
 
16.1Yes 
16.2NoPage Valet only sees a snapshot; Site Valet QA service supports this checkpoint
16.3Yes 
26.4YesTests are based on detailed analysis in Section 508
26.5Yes 
 
17.1NoTo be fixed; tests exist and are already supported for Section508 testing
27.2ImpliedViolations in markup will be shown as validation errors
27.3NoSee #7.1 above
27.4Yes 
27.5Yes 
 
18.1ImpliedSee #6 and #9
 
19.1Yes 
29.2PartialSee #6.4 for scripts; #7.1 for other content
29.3ImpliedSee #6.4
39.4Yes 
39.5Yes 
 
210.1YesCannot detect all violations
210.2Yes 
310.3NoViolations will generate other warnings; see #5.
310.4No 
310.5No 
 
211.1NoOther Site Valet tools support this
211.2ImpliedSee #3.2, #3.3, etc.
311.3NoOther Site Valet tools support this
111.4NoThis would be paradoxical in a test tool!
 
112.1Yes 
212.2No 
212.3No 
212.4Yes 
 
213.1No 
213.2Yes 
213.3NoSee other Site Valet tools
213.4No 
313.5No 
313.6Yes 
313.7No 
313.8No 
313.9No 
313.10No 
 
114.1No 
314.2No 
314.3Yes