#back-to-top:after {
content: '\f077';  
line-height: 36px; }
#back-to-top { 
background: #f9a825;
color: #fff;
transition: all 0.25s ease-in-out;
}
#back-to-top:hover {
background: #222;
}
#back-to-top {  
position: fixed;
bottom: 10px;
right: 10px;
z-index: 1;
width: 40px;
height: 40px;
text-align: center;  
cursor: pointer;
border: 0;
border-radius: 50%;
text-decoration: none;
opacity: 0;
}
#back-to-top:after {
font-family: FontAwesome;
}
#back-to-top.show {
opacity: 1;
}