Validators
- W3C CSS Validation Service
- W3C Markup Validation Service
- W3C mobileOK Checker
- WDG CSSCheck
- WDG HTML Validator
- (X)HTML5 Validator
HTML5 support
- The HTML5 Test
- CSS3 & HTML5 Browser Support
- When can I use...
- HTML5 compatibility
- HTML5 & CSS3 READINESS
Web site analysis
- nibbler: gives a report scoring the website out of 10 for various important criteria including accessibility, SEO, social media and technology.
- SiteReport Card: provides detailed reports on various aspects of your web pages including HTML validation, broken links, load time analysis, etc.
Boilerplates
- HTML5 Boilerplate: HTML5 Boilerplate is the professional frontend developers's base HTML/CSS/JS template for a fast, robust and future-safe site.
- Initializr: It generates templates based on HTML5 Boilerplate by allowing you to choose which parts you want or don't want from it.