CSS HTML Validator Professional

CSS HTML Validator (formerly CSE HTML Validator) includes an unusually powerful custom syntax checking engine specifically designed to check HTML, XHTML, CSS, SEO and more.
CSE HTML Validator helps eliminate website problems.

CSS HTML Validator from AI Internet Solutions includes:

• HTML / HTML5 / / XHTML Validator
• CSS / CSS3 Validator
• PHP Controller
• JavaScript Linter
• Link Checker
• Spellchecker
• Accessibility Checker
• Search Engine Optimization (SEO)
• CSS editor
• HTML Editor
• XHTML Editor
• and moho more.

CSS HTML Validator protects your privacy by not sending your HTML and CSS documents over the Internet. This also means that Internet access is not required.

Here is a table of differences between versions
https://www.htmlvalidator.com/htmlval/comparisonchart.html