Valid HTML markup (parsing-validity)

Ensure the page validates against the formal specification of its declared markup language (e.g., HTML5). Avoid errors such as missing end tags, duplicate IDs, or improperly nested elements.


Invalid HTML structure

This page is missing a <!DOCTYPE> declaration and contains parsing errors.


Here is some content

First paragraph with duplicate ID

Second paragraph with same ID

This div should not be inside a span

Note: Possible to automatically test. Parsing errors like missing doctype, unclosed tags, duplicate IDs, and invalid nesting can be detected automatically.

axe detected: none  |  QualWeb detected: 4.1.1