* {box-sizing: border-box;}

body { 
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background-color: #EEEEEE;
  width: 100%;
}

.header {
  overflow: hidden;
  background-color: #FFCCCC;
  padding: 2px 2px;

}
.footer {
 /* overflow: hidden;*/
  position:absolute;
  background-color: #99FF99;
  padding: 2px 2px;
  vertical-align: middle;
  bottom:0;
  left: 0;
  width: 100%;

}

.main {
  overflow: hidden;
  background-color: #EEEEEE;
  padding: 250px;
  
}
.principal{
  text-align: center;
  margin: auto;

}

.botonmenuprinci{

  padding: 32px 35px;
  background-color:#9eaca6;
  text-decoration: none;
  color: black;
}

.usu {
  overflow: hidden;
  background-color: #EEEEEE;
  text-align: left;
}
.bandera {
  overflow: hidden;
  background-color: #EEEEEE;
  text-align: left;
}
.header a {
  float: left;
  color: black;
  text-align: center;
  padding: 12px;
  text-decoration: none;
  font-size: 18px; 
  line-height: 25px;
  border-radius: 4px;
}

.header a.logo {
  font-size: 25px;
  font-weight: bold;
  vertical-align: middle;
}
.footer a.logo {
  font-size: 15px;
  vertical-align: middle;
  text-align: left;
}
.footer a.logo2 {
  font-size: 15px;
  vertical-align: middle;
  text-align: right;
}
.header img {
  font-size: 25px;
  font-weight: bold;
  vertical-align: middle;
  width: 220px;
}
.footer img {
  font-size: 25px;
  font-weight: bold;
  vertical-align: middle;
  width: 50px;
}
.usu img {
  vertical-align: middle;
  width: 90px;
}
.principal img {
  vertical-align: middle;
  
}
.bandera img {
  vertical-align: middle;
  width: 40px;
}

@media screen and (max-width: 500px) {
  .header a {
    float: none;
    display: block;
    text-align: left;
  }
  
  .header-right {
    float: none;
  }
}