body{
    margin: 0;
    background-image: url("htask4.jpg");
    background-repeat: repeat;
    background-size: 3000px 1000px;
}
ul{
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    background-color: none;
}
ul li{
    float: left;
}
ul li a{
    display: block;
    color: white;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
    font-size: 19px;
}
ul li a:hover{
    background-color: blueviolet;
    color: white;
}
.abc{
    margin-top: 20px;
    margin-right: 500px;
    margin-left: 80px;
    height: 850px;
    width: 500px;
    border-style: dashed;
    border-color: rgb(82, 80, 80);
}
.flex-container {
  display: flex;
  flex-direction: column;
  background-color: none;
}
.flex-container > div {
  background-color: none;
  margin-top: 20px;
    margin-right: 500px;
    height: 850px;
    width: 500px;
  text-align: center;
  line-height: 75px;
  font-size: 20px;
  color: white;
}
 .one{
    margin-top: 120px;
    margin-right: 500px;
    margin-left: 80px;
    height: 800px;
    width: 500px;
    border-style: dashed;
    border-color: rgb(82, 80, 80);
    color: white;
    font-size: 20px;
    text-align: center;
} 
a:hover {
  color: yellow;
  font-size: 18px;
}