HTML Checking for Large Sites

Rocket Validator automatically scans your sites for accessibility issues using the W3C Validator,
hosted on our own servers and integrated into our web crawler.

Try Rocket Validator Pro

HTML issues tagged as sizes.

The “sizes” attribute may be specified only if the “srcset” attribute is also present.
When the “srcset” attribute has any image candidate string with a width descriptor, the “sizes” attribute must also be present.