Parsing of Content

Overview and General Guidelines

Ensure that user agents, including assistive technologies, can accurately interpret and parse content.

If the content cannot be parsed into a data structure, then different user agents may present it differently or be completely unable to parse it.

Some user agents use "repair techniques" to render poorly coded content.

Since repair techniques vary among user agents, authors cannot assume that content will be accurately parsed into a data structure or that it will be rendered correctly by specialized user agents, including assistive technologies, unless the content is created according to the rules defined in the formal grammar for that technology.

In markup languages, errors in element and attribute syntax and failure to provide properly nested start/end tags lead to errors that prevent user agents from parsing the content reliably.

In content implemented using markup, elements should have complete start and end tags, elements are nested according to their specifications, elements do not contain duplicate attributes, and any IDs are unique, except where the specifications allow these features.

Ensuring that Web pages have complete start and end tags and are nested according to specification helps ensure that assistive technologies can parse the content accurately and without crashing.

WCAG Related Guidelines

4.1.1 Parsing (Level A)