What does this mean?

Heading elements (<h1>, <h2>, ...) must contain some machine-readable text content.

Heading should never be empty, or just contain whitespace:

<h1>   </h1>

Headings which contain images or other media must specify alternative text:

    <img src="heading.png" alt="Press releases"> 

See Technique H42 for more details.

99.2% done

How close this website is to fixing this issue.

HTML Found on page Issues
<h3 class="NelComponents__Heading-vsly48-4 dbZXkj nel-Typography-454 nel-Typography-449" data-ref="heading"></h3> 4
4 distinct issues were found in the sample of 125 web pages.
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