Content does show inaccessible examples

I can’t comment on everything, but there are a lot of inaccessible examples on the pages, for example:

<html> element is listed without a language specified. http://marksheet.io/html-valid-document.html#the-html-element
Images: No alt attribute shown or explained. http://marksheet.io/html-images.html
Tables: Need at least scope attributes or headers and ids in some instances. http://marksheet.io/html-tables.html
Forms: Should have labels in the early examples as well. There is no point in using unlabelled form elements. Labels are often not associated using for and id which makes them useless. http://marksheet.io/html-forms.html

jgthms / marksheet