index.css

*
{
margin:0;
padding:0;
}

header {
background-image: linear-gradient(rgba(24, 179, 153, 0.5), rgba(0,0,0,0.5)),url('nature.jpeg');
height:100vh;
background-size:cover;
background-position:center;
}

.nav-menu {
float: left;
list-style:none;
margin-top:30px;
}

.nav-menu li {
display: inline-block;
}

.nav-menu li a {
color:rgb(255, 255, 255);
text-decoration: none;
padding:5px 20px;
font-family:"Verdana", "sans-serif";
font-size:20px;
}

.homebtn a {
border: 1px solid black;
background-color:rgb(5, 0, 0);
}

.nav-menu li a:hover {
border:1px solid black;
background-color: rgb(0, 0, 0);
}

.tagline {
position: absolute;
width:1200px; 
margin-left:0;
margin-top:0;
}

h1 {
color:white;
font-size:48px;
font-family:"Verdana", "sans-serif";
text-align:center;
margin-top:275px;
}

.adopt {
margin-top:30px;
margin-left:540px;
}

.bttn {
border: 1px solid white;
padding:10px 30px;
color:yellow;
font-family:"Verdana", "sans-serif";
font-size: 20px;
text-decoration:none;
}

.adopt a:hover {
background-color: rgb(5, 5, 5);
}