.clearfix:after {
  content: "";
  clear: both;
  display: block;
}
ul {
  padding: 10px;
}
li {
  list-style: none;
}
a, a:hover, a:visited{
  text-decoration: none; 
  color: inherit;
}
.tab-list {
  margin: 0;
  padding: 0;
}
.tab {
  cursor: pointer;
  float: left;
  padding: 4px 20px;
}
.tab.active{
  background-color: gray;
  color: white;
}
.tab-content {
  display: none;
}
.tab-content.active {
  display: block;
  padding: 20px;
  border: 1px solid gray;
}