Search Engine Forums, SEO Forum

As far as clean code ranking well, I don't think google pays much attention to that but I may be wrong. For now content is king [and IMHO it will stay that way].

Clean Code is vital for validation. It is done through the HTML Validators, Cascading Style Sheet Validators, Link Checkers.

It will not compliant fully if you validate the website code, instead it will eliminate the basic coding errors which will cause problems.

Maintaining clean code and accessible pages will help your page be visible in other devices.

Maybe some had changed their contents and still indexed on Google's cache. Surely there is something that like domain age, backlinks, etc that makes the site rank.