html, body {
    height: 100%;
}

html {
    display: table;
    margin: auto;
}

body {
    display: table-cell;
    vertical-align: middle;
    background-color: #eeeeee;
}

.fajfr {
   text-decoration: none;
   color: black;
}

.fajfr:hover {
    text-decoration: none;
    color: black;
}

.jumbotron {
    background-image: url(headcrab.png);
    background-size: 20%;
    background-repeat: no-repeat;
    background-position: right;
}

         
.butnik {
    background-image: linear-gradient(to right, #24C6DC 0%, #514A9D  51%, #24C6DC  100%);
    margin: 10px;
    padding: 15px 45px;
    text-align: center;
    text-transform: uppercase;
    transition: 0.5s;
    background-size: 200% auto;
    color: white;            
    box-shadow: 0 0 20px #eee;
    border-radius: 10px;
    display: block;
}

.butnik:hover {
    background-position: right center; 
    color: #fff;
    text-decoration: none;
}