W3C Markup Validation Service - Validates HTML markup of web pages, one at a time.
KNOW App - KNOW is a leading mobile productivity platform helping companies digitize daily checklists, tasks, shifts, attendance, data collection, and much more.
Rocket Validator - Site-wide Accessibility and HTML validation made easy. With a single click, Rocket Validator will check thousands of web pages on your site for Accessibility and HTML conformance, producing a detailed, actionable report on seconds.
GoAudits - A professional mobile app for operations management & inspections. Improve standards, control quality, verify safety. Build digital checklists and go paperless now.
HTML Validator - HTML Validator is a Mozilla extension that adds HTML validation inside Firefox and Mozilla.
Your Life In Weeks - A spreadsheet of your life inspired by Wait But Why