0. Write HTML

This book starts with a “Chapter 0,” because I like to start with this point without depriving you of a chapter.

1 <div class="col-xs-12 col-sm-12 col-md-12 col-lg-12 div-slideshow">
2   <h7>
3     SOME TEXT I CHANGE TO <h7 style="color: white;">MAKE IT ANONYMOUS</h7>.
4   </h7>
5 </div>

(Via and with friendly permission by Geoffrey Crofte.)

You already know what’s coming.

Those class names; really, those class names (👀 div-slideshow).

The <h7>; even nested <h7>.

The <h7>, no matter whether it’s nested.

There is no <h7> element in HTML. The buck stops with <h6>.

But isn’t this obvious?

As you can tell, it’s not. This is HTML that our peers are writing—that professional frontend developers are writing.

They write it because they had not been trained to validate their code. To validate, through the classic W3C validator (same core for living HTML as validator.nu), or one of the various packages. To validate, because that’s what we as professional frontend developers do. Everyone can write invalid HTML. Professional frontend developers write valid HTML—because only valid HTML is HTML.