body,
html {
  padding: 2.5em;
  height: 100%;
}

.title404 {
  text-align: center;
  font-size: 3em;
}

.content404 {
  text-align: center;
  font-size: 2.5em;
}

.c404img {
  display: flex;
  justify-content: center;
}

.c404img img {
  filter: opacity(25%) blur(10px);
}

footer {
  position: absolute;
  bottom: 0;
  margin: 2.5em;
}