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.
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.
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.
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
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.
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.
Every clause in the Section 508 guidelines is explicitly tested. Where a possible violation is detected, a warning is displayed.
|1||1.1||Yes||Several tests for aspects of this, not just the usual test for ALT attributes.|
|1||1.2||Implied||Dealt with under #9.1|
|2||3.2||Yes||Validation is rigorous and formally correct|
|2||3.6||Implied||Violations will be shown as validation errors|
|1||4.1||No||We cannot detect changes in language|
|1||5.2||Yes||Test is limited|
|2||5.3||Implied||Violations will generate warnings from other tests|
|1||6.2||No||Page Valet only sees a snapshot; Site Valet QA service supports this checkpoint|
|2||6.4||Yes||Tests are based on detailed analysis in Section 508|
|1||7.1||No||To be fixed; tests exist and are already supported for Section508 testing|
|2||7.2||Implied||Violations in markup will be shown as validation errors|
|2||7.3||No||See #7.1 above|
|1||8.1||Implied||See #6 and #9|
|2||9.2||Partial||See #6.4 for scripts; #7.1 for other content|
|2||10.1||Yes||Cannot detect all violations|
|3||10.3||No||Violations will generate other warnings; see #5.|
|2||11.1||No||Other Site Valet tools support this|
|2||11.2||Implied||See #3.2, #3.3, etc.|
|3||11.3||No||Other Site Valet tools support this|
|1||11.4||No||This would be paradoxical in a test tool!|
|2||13.3||No||See other Site Valet tools|