Clean code

[Vincibean]

I've noticed some weird HTML tags that my browser (Firefox) doesn't seem to be able to parse, so it would be better to check if these tags are actually valid tags.
While developing, I noticed that sometimes the HTML of the page is invalid, but the browser manages to adjust; it would be better to check if all the pages are valid now.
Also, I suspect that some of the CSS and JS files aren't used and could be deleted (or included, if they seem useful; e.g. readingTime.min.js).
Finally, I guess that some HTML comments can be removed.