#back-button{
  display: flex;
  align-items: center; /*This is how you set something on the y axis using css*/
  justify-content: center; /*This is how you set something on the x axis using css*/
  color: #fff;
  background:blue;
  height: 60px;
  font-weight: bold;
  text-decoration: none;
  text-transform: uppercase;
  z-index:10; /*z-index is how you make elements appear on top of others using a numerical value*/
  top: 0;
  left: 0;
  list-style: none;
  display: flex;

}

#back-button a:hover{
  color: #fff;
  position: relative;
  width: 100%;
  text-align: center;
  display: inline-block;
}
#back-button a:visited{
  color: #fff;
}