Démonstration de position fixe

#parent {
	border: 0.3em solid #336; background: #AAD;
	width: 50%; margin: auto;
	position: relative; /* ancêtre positionné */
}
#cadet { border: 0.1em solid #F33; }
#enfant {
	border: 0.3em solid #669; background: #DDF;
	top: 0.5em; left: 0.5em;
	position: fixed;
}