Your website should comply with best practices and standards for coding. Any significant errors in code should be fixed.
What to do:
- Make sure all elements have start (open) and end (close) tags
- Have all HTML elements nested correctly
- Make sure elements must not contain duplicate attributes
- Make sure element IDs must be unique
- Markup Validator (check for errors in your code – not all, in fact many errors won’t be relevant for accessibility and some errors won’t show)
- How to fix HTML with examples
Plain English Explanation:
This is a very broad and sweeping requirement. It makes sure that browsers, screen readers, and other assistive technologies can analyze and make your website’s code understandable (“parse” is the technical word) so that your website is rendered correctly.
Many browsers can go past errors and still render a website correctly but it’s bad practice to rely on browsers and assistive technologies to interpret incorrect code.
What 4.1.1 boils down to is making sure your website’s code is fundamentally sound by checking and testing.
Developers should look over and check your code.
Everyone should test your website, especially using screen readers, to make sure it renders correctly.
The markup validator above will help with catching some errors but it is not a substitute for a manual examination of your code.
The most important takeaway here is to make sure your website is free of any major coding errors that prevent assistive technologies like screen readers from accurately rendering your website.
Note: Assistive technologies are any technologies that help persons with disabilities access the web. Screen readers are the most common assistive technology but others include screen magnification software, text readers, voice to text or speech input software, and other devices that facilitate input.