.github {
background-image: url(../IMG/github.png);
width: 40px;
height: 40px;
display: block;
text-indent: -9999px
}
.linkedin {
background-image: url(../IMG/linkedin.png);
width: 40px;
height: 40px;
display: block;
text-indent: -9999px
}
.twitter {
background-image: url(../IMG/twitter.png);
width: 40px;
height: 40px;
display: block;
text-indent: -9999px
}