Rocket Validator automatically checks your pages on the W3C Validator.
ontouchstart attribute, used in devices with a touch screen, and not supported by all browsers, is not a valid attribute in the current HTML5 standard.
You can consider replacing it with the more generic
onclick attribute, or still use it if you’re OK with its limitations.
When was the last time you validated your whole site?
Keep your sites healthy checking for A11Y/HTML issues on an automated schedule.