Each CSS snippet should have a card-like layout with the CSS syntax wrapped in an HTML pre element. Each CSS snippet can easily be highlighted for copying on click using the CSS user-select property.

"," ",".row {"," display: flex;"," flex-direction: row;"," flex-wrap: wrap;","}"," "," "," "," Flexbox column "," ...

By appending just a few lines of HTML and CSS code, researcher Louis Dion-Marcil showed how an external sender could hide the very warning from an email message.