Checks that an icon is defined in the HTML for the 16x16 size.
The favicon.ico file is a legacy format that you should include, but for modern web browsers it is better to provide an optimized PNG image. You can do this by including a <link> tag in the <head> of the webpage. The website should define several different sizes for different purposes. One of those sizes is the 16x16 pixel size. The following code is our recommendation.
<link rel="icon" type="image/png" sizes="16x16" href="/favicon-16x16.png">
This test will check for the presence of a <link> tag with the appropriate size and then download the image to make sure it is the proper size and format.