2.2 - Technical check methodology

To evaluate web page conformance with the requirements, an evaluation methodology is suggested that uses automatic and semi-automatic instruments and draws on the knowledge of the technical expert involved. It borrows from the methodology proposed by W3C and includes the following steps:

• Use of automatic validation systems to evaluate the degree to which the language used conforms to its formal definition. The validation service provided by W3C is worthy of note.
• Use of semi-automatic accessibility evaluation instruments to identify problems that are not revealed by automatic checks. A list of the most widely used instruments can be found on the Evaluation, Repair, and Transformation Tools for Web Content Accessibility page of the W3C site.
• Expert evaluation of the use of elements and attributes in accordance with the language specifications. For example, in HTML, Header elements are used to structure content and not to obtain graphic effects. In CSS, units of measurement are used that enable users to view content according to their display preferences.
• Examination of the page using different graphics browsers, in different versions and operating systems to verify that:

  a) the content and functionality in a page are the same in the different browsers;

  b) page presentation is similar in all the browsers that support the technologies indicated at requirement 1;

  c) if image loading is switched off, page content and functionality can still be used;

  d) if sound is switched off, the content of any audio file can be used in another form;

  e) using the controls available in browsers to define font size, page content can still be accessed;

  f) the page can be navigated in an easily understandable way using the keyboard alone;

  g) page content and functionality can still be accessed (including in equivalent fashion) when style sheets, scripts, applets and objects are disabled.

• Ensure that foreground and background colour combinations provide sufficient contrast, according to the following algorithms suggested by W3C:
  • Brightness difference.
    
    

    Calculate colour and background brightness using the following formula:

    ((Red X 299) + (Green X 587) + (Blue X 114)) / 1000

    in which Red, Green and Blue are the decimal values of the colours. It is recommended that the range for colour brightness difference should be greater than 125.

  • Colour difference
    
    

    [Max (Red1, Red2) - Min (Red1, Red2)] + [Max (Green1, Green2) - Min (Green1, Green2)] + [Max (Blue1, Blue2) – Min (Blue1, Blue2)]

    in which Red, Green and Blue are the decimal values of the colours and Max and Min the maximum and minimum values in the given range. It is recommended that the colour difference range should be greater than 500.

    Programs are available to help assess the degree to which the selected colours correspond to the algorithm (example).

• Examine the page with a text browser and check that:
  • content and functionality are available (including in equivalent form) in the same way as in graphics browsers;
  • page content maintains its overall meaning and semantic structure.

The evaluation ends in the preparation of a report in which the technical expert states the compliance of the Web page with every single requirement.

The technical expert should be a Web-technology professional with appropriate experience and knowledge of the issues and accessibility techniques equivalent to those provided by W3C – WAI in its Education & Outreach program.