CSS layout and flexbox-Assessment

*, *:before, *:after {
  box-sizing: border-box;
}

* {
  margin: 0;
  padding: 0;
  border: 0;
  outline: 0;
  font-size: 100%;
  vertical-align: baseline;
  background: transparent;
}
a {
  color: white;
  text-decoration: none;
}
nav{
  background-color: #2E2D2B;

}
.nav-row {
  display: flex;
  flex-wrap: wrap;
  flex-flow: row;
  list-style-type: none;
}
li {
  border: 1px solid #2E2D2B;
  width: 300px;

  padding: 20px;
  text-align: center;
}
.header-content {
  display: block;
  flex-wrap: nowrap;

  background-image: url("../img/header-img.jpg");
  background-size: cover;
  background-position: center center;
  position: block;

  padding: 45px 0px 200px 0px;
  text-align: center;

  width: 1425px;
}
.main-heading {
  font-family: 'Josefin Sans';
  font-size: 100px;

  padding: 50px 0 0 0;
  line-height: .5;
}
.sub-heading {
  font-family: 'Dancing Script';
  font-size: 54px;
  color: #F1F0F2;
  line-height: .7;
}
main {
  display: flex;
  flex-direction: row;
  align-items: flex-start;

  background-color: #FEF9EC;

  width: 900px;
  border: 1px solid white;

  position: relative;
  top: -45px;
  margin: auto;

  box-shadow: 0px 3px 3px rgba(0,0,0,.75);
}
.blog-row {
  display: flex;
  flex-wrap: wrap;
  flex-direction: row;

  padding: 50px;
  margin: 50px 10px 10px 10px;

  width: 60%

  background-color: white;

  text-align: left;
  font-family: 'Josefin Sans';
  font-size: 24px;

  box-shadow: 0px 3px 3px rgba(0,0,0,.75);
}
aside {
  display: flex;
  flex-wrap: wrap;
  flex-direction: row;

  background-color: white;

  padding: 50px;
  margin: 50px;

  width: 40%

  text-align: left;
  font-family: 'Josefin Sans';
  font-size: 24px;

  box-shadow: 0px 3px 3px rgba(0,0,0,.75);
}
#dino {
  background-image: url("../img/dino.jpg");
  background-position: center center;
  background-size: cover;

  height: 200px;
  width: 200px;

  float: right;
}
#xx {
  background-image: url("../img/xx.png");
  background-position: center center;
  background-size: cover;

  height: 200px;
  width: 200px;

  float: right;
}
#yhact {
  background-image: url("../img/yhact.jpg");
  background-position: center center;
  background-size: cover;

  height: 200px;
  width: 200px;

  float: right;
}
.auth-pic {
  background-image: url("../img/author.jpeg");
  background-position: center center;
  background-size: cover;

  height: 200px;
  width: 200px;

  float: right;

  padding:
}
footer {
  background-color: #333333;
}
footer > span {
  display: block;

  color: white;

  padding: 15px;
  text-transform: uppercase;
  text-align: center;
}