body {
  margin: 1em;
  max-width: 800px;
}
.post {
  margin: 1em 0;
  clear: both;
}
.post p.key {
  float: left;
  margin: 0 1em 1em;
}
.post p.message {
}
img,
iframe,
audio,
video {
  max-width: calc(100% - 100px);
  height: auto;
}