A valid source code

Impact: Low to moderate

Users mainly impacted: Blind, visually impaired, motor impaired.

RGAA criteria: Criterion 8.1 [A] - Criterion 8.2 [A]


Assistive technologies are based on page code (DOM) for rendering and interaction with the user. If the HTML code contains code errors, this may render some systems inoperative.

Declare the DTD correctly

It is important to Add a Doctype declaration. This makes sure the document will be parsed the same way by different browsers.

Doctype HTML5

<!DOCTYPE html>

Other doctype declarations

A valid source code

To validate your source code, always use the generated source code (with JavaScript) with the W3C online validation tool.

The online tool outputs two types of results: warnings and errors. Only errors are to be taken into account. Moreover, the source code does not necessarily have to be 100% valid for accessibility, only the points impacting accessibility must be corrected. For example, errors relating to the writing of URLs are not considered accessibility errors.

A source code is valid when:

  • tags respect the writing rules (tags are in accordance with the type of document declared);
  • the nesting of the tags is compliant (for example, no link nested in another link);
  • the opening and closing of the tags are in conformity
  • the attributes respect the writing rules (for example, no obsolete elements are present);
  • the attribute values respect the writing rules (for example, duplicate ID values are not compliant).