html, body {
	height: 100%;
	min-height: 100%;
	margin: 0;
	text-align: center;
	position: relative;
}
.slide {
	min-height:100%; 
	position:relative;
}
.slide a {
	position: absolute;
	top: 50%;
	height: 10em;
	margin-top: -5em;
}
#slide1 {
	background: peachpuff; 
}
#slide2 {
	background: lightcoral;
}
#slide3 {
	background: lightgray;
}
#slide4 {
	background: lightgreen;
}

html, body {
	height: 100%;
	min-height: 100%;
	margin: 0;
	text-align: center;
	position: relative;
}
.slide {
	min-height:100%; 
	position:relative;
}
.slide a {
	position: absolute;
	top: 50%;
	height: 10em;
	margin-top: -5em;
	margin-left: -3em;
}
#slide1 {
	background: peachpuff; 
}
#slide2 {
	background: lightcoral;
}
#slide3 {
	background: lightgray;
}
#slide4 {
	background: lightgreen;
}

Update css for centering slide text horizontally
Update css for centering slide text horizontally