Favicon Image Sizes
Tests that the favicon contains 16x16 and 32x32 icons.
If you configure your Favicons according to our recommendations the favicon.ico file will only be used by Internet Explorer, and the only sizes it uses are 32x32 and 16x16. Therefore, we recommend including both the 16x16 and 32x32 sizes inside the favicon.ico file. This test will produce a warning if either of these sizes are missing. Even if you don't want to support old versions of IE, you should still make a favicon.ico file because other browsers and services (like search engines) may look for it if they can't find the website's icon in another place.
You are welcome to include additional sizes, but we recommend against it because it will unnecessarily increase the filesize and thus impact performance.
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