Exemple de code du sélecteur CSS :first-line.

<style type="text/css">
.exemple { border: 1px solid #666; margin-bottom:10px; padding:5px; }

.exemple-first-line-simple:first-line { text-decoration : underline; color : green}
.exemple-first-line-double::first-line { text-decoration : line-through; color : green}
</style>

<div class="exemple">sans first-line sans first-line sans first-line sans first-line sans first-line sans first-line<br>sans first-line sans first-line</div>
<div class="exemple exemple-first-line-simple">:first-line :first-line :first-line :first-line :first-line :first-line<br>:first-line :first-line</div>
<div class="exemple exemple-first-line-double">::first-line ::first-line ::first-line ::first-line ::first-line ::first-line<br>::first-line ::first-line</div>