html { 
  background: url(bg_gl.jpg) no-repeat center center fixed; 
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
  font-size: 30px;
  font-family: Tahoma;
}

.container {
display: flex;
justify-content: center;
align-items: center;
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
}

.centered-element {
width: 600px;
height: 155px;
}