Valid Markup

The rules of the HTML used to create web pages are straightforward, but there are several HTML types and the rules vary by type. The good news is that your web page specifies its HTML type, and automated testing provides a quick and efficient way to check the validity of your page.

Why Valid Markup is Important

Assistive technology like screen readers relies on web pages obeying the rules of HTML.

Beyond this, valid markup:

  • ensures a consistent and expected display appearance
  • helps search engines index and rank your pages
  • minimizes unintended behaviors in highly interactive pages

How to Check If Markup is Valid

You can check your pages via one of these free tools:

  • W3C's Markup Validation Service is a web page checker that offers line-based error reporting and suggestions for correct HTML

  • Deque axe Expert is a Chrome extension that provides fuller error explanations and resolution techniques

Both tools will find errors; you or technical staff will need to make the fixes in your HTML.