Check for invalid HTML

[nsmsn]

I mistakenly had commas separating class names in my HTML and so <div class="h-card, p-author, v-card">` did not register an hCard on indiewebify.me. With some help from others, I quickly fixed myself.

If Indiewebify is able to detect invalid HTML like that, maybe it would be helpful to suggest removing commas or other invalid characters from the markup if anyone else is making HTML mistakes.