*{
    padding: 0;
    margin: 0;
}
body {
  background-image: url(pliki/metro.jpg);
  background-size: 100%;
}
main, #nav, footer {
  width: 75%;
  max-width: 1000px;
  margin: 0 auto;
}
main, footer{
  background-color: rgb(234, 238, 245);
}

.sectionHeader {
  text-align: center;
  border-top: black 2px solid;
  background: linear-gradient(180deg, #ff0000, #000000);
  color: rgb(229, 222, 222);
  font-weight: bold;
  font-size: 24px;
  padding: 10px 20px;
  text-transform: uppercase;
  letter-spacing: 2px;
  box-shadow: 0 3px 6px rgba(0, 0, 0, 0.3);
}