CSS transition fade in

CSS Keyframes support is pretty good these days:

.fade-in {
	opacity: 1;
	animation-name: fadeInOpacity;
	animation-iteration-count: 1;
	animation-timing-function: ease-in;
	animation-duration: 2s;
}

@keyframes fadeInOpacity {
	0% {
		opacity: 0;
	}
	100% {
		opacity: 1;
	}
}

<h1 class="fade-in">Fade Me Down Scotty</h1>