Another one is 'use the correct status codes for page requests'. Seen far too many sites returna 200 OK status for a non existent page, which may cause havoc w

Another one is 'use the correct status codes for page requests'. Seen far too many sites returna 200 OK status for a non existent page, which may cause havoc with search engines indexing 404 messages and what not. Oh, and make sure you actually use heading tags properly. God, so many sites and apps seem to be designed with no thought put into heading structure, with random h2s and h3s strewn about at random. Especially don't forget the h1 tag, and try and make sure it (and the title tag for the page) are both unique on every page. Basic I know, but come on. Too many SPAs seem to be built with no thought put into even the basics of HTML structure or on page SEO.