body {
  background-color: black;
  margin: 0 auto;
  padding-bottom: 10px;
}

a:link {
  color: yellow;
  background-color: transparent;
  text-decoration: none;
}

a:visited {
  color: yellow;
  background-color: transparent;
  text-decoration: none;
}

a:hover {
  color: yellow;
  background-color: transparent;
  text-decoration: underline;
}

a:active {
  color: yellow;
  background-color: transparent;
  text-decoration: underline;
}

h1 {
  color: white;
  text-align: center;
}

h2 {
  color: white;
  text-align: center;
}
h3 {
  color: white;
  text-align: center;
}
h4 {
  color: white;
  text-align: center;
}
p {
  font-family: verdana;
  font-size: 20px;
  color: white;
  text-align: center;
}
pre {
  font-family: verdana;
  font-size: 20px;
  color: white;
  text-align: center;
}
iframe {
  text-align: center;
}
.header-image {
  display: block;
  margin-left: auto;
  margin-right: auto;
  width: 90%;
}

.optimal-settings {
  display: block;
  margin-left: auto;
  margin-right: auto;
  width: 90%;
}

.footer {
  text-align: center;
  padding: 10px;
}
.align-left-box {
  margin: auto;
  width: 90%;
}
.align-center-box {
  display: flex;
  justify-content: center;
}