The :target pseudo-class
:target matches the element addressed by the URL fragment. That makes deep-linked highlights, notes, and simple panels possible without storing state in JavaScript.
<a href="#shipping">Shipping details</a>
<section id="shipping">…</section> #shipping {
border: 1px solid transparent;
}
#shipping:target {
border-color: currentColor;
} Fragments enter browser history and should identify useful destinations. Avoid hiding essential content unless there is an equally clear way to reveal it.