div#principal {
  position:relative;
  top:0;
  left:0;
}

div#mensaje {
  background: #fff;
  font-size: 1.2em;
  text-align: right;
  width: 30%;
  padding-left: 3%;
  top:0;
  left:0;
  float:left;
}

p#centro {
  height: 300px;
  background: transparent url(../imagenes/edificio.jpg) no-repeat center center;
  top:0;
  left:34%;
  width: 24%;
  margin-left: 3%;
  margin-right: 3%;
  float:left;
}

div#noticias {
  background: #fff;
  top:0;
  left:67%;
  width: 30%;
  padding-right: 3%;
  margin-bottom: 3%;
  float:left;
}

div#noticias div p, div#noticias div ul {
  font-size: 0.8em;
  margin-top: 0px;
  padding-top: 0px;
  margin-bottom: 0px;
  padding-bottom: 0px;
}
div#noticias div p:first-child {
  font-size: 1em;
  margin-top: 10px;
}