W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
body, html {
  height: 100%;
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
}

* {
  box-sizing: border-box;
}

.bg-image {
  /* Full height */
  height: 50%; 
  
  /* Center and scale the image nicely */
  background-position: center;
  background-repeat: no-repeat;
  background-size: cover;
}

/* Images used */
.img1 { background-image: url("img_snow.jpg"); }
.img2 { background-image: url("img_girl.jpg"); }
.img3 { background-image: url("img_lights.jpg"); }
.img4 { background-image: url("img_nature.jpg"); }
.img5 { background-image: url("img_forest.jpg"); }
.img6 { background-image: url("img_woods.jpg"); }

/* Position text in the middle of the page/image */
.bg-text {
  background-color: rgb(0,0,0); /* Fallback color */
  background-color: rgba(0,0,0, 0.4); /* Black w/opacity/see-through */
  color: white;
  font-weight: bold;
  font-size: 80px;
  border: 10px solid #f1f1f1;
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  z-index: 2;
  width: 300px;
  padding: 20px;
  text-align: center;
}
</style>
</head>
<body>

</body>
</html>

​x
 
<!DOCTYPE html><html><head><meta name="viewport" content="width=device-width, initial-scale=1"><style>body, html {  height: 100%;  margin: 0;  font-family: Arial, Helvetica, sans-serif;}​* {  box-sizing: border-box;}​.bg-image {  /* Full height */  height: 50%;     /* Center and scale the image nicely */  background-position: center;  background-repeat: no-repeat;  background-size: cover;}​/* Images used */.img1 { background-image: url("img_snow.jpg"); }.img2 { background-image: url("img_girl.jpg"); }.img3 { background-image: url("img_lights.jpg"); }.img4 { background-image: url("img_nature.jpg"); }.img5 { background-image: url("img_forest.jpg"); }.img6 { background-image: url("img_woods.jpg"); }​/* Position text in the middle of the page/image */.bg-text {  background-color: rgb(0,0,0); /* Fallback color */  background-color: rgba(0,0,0, 0.4); /* Black w/opacity/see-through */  color: white;  font-weight: bold;  font-size: 80px;  border: 10px solid #f1f1f1;  position: fixed;  top: 50%;  left: 50%;  transform: translate(-50%, -50%);  z-index: 2;  width: 300px;