Header is disappearing after adding responsive CSS.

<p>@media screen and (min-width: 660px) {

/***********************
 HEADER
***********************/

  nav {
    background: none;
    float: right;
    font-size: 1.125em;
    margin-right: 5%;
    text-align: right;
    width: 45%;
   }

  #logo {
    float: left;
    margin-left: 5%; 
    text-align: left;
    width: 45%;
  }

  h1 {
    font-size: 2.5em;
    }

  h2 {
    font-size: 0.825em;
    margin-bottom: 20px;
    }

  header {
    border-bottom: 5px solid #599a68;
    margin-bottom: 60px;
  }

} </p>

<p>/***********************
GENERAL
***********************/

body {
  font-family: 'Open Sans', sans serif;
}

#wrapper {
  max-width: 940px;
  margin: 0 auto;
  padding: 0 5%;
}


a {
  text-decoration: none;
}

img {
  max-width: 100%;
}

h3 {
  margin: 0 0 1em 0;
}


/***********************
HEADING
***********************/

header: {
  float: left;
  margin: 0 0 30px 0;
  padding: 5px 0 0 0;
  width: 100%;
}

#logo {
  text-align: center;
  margin: 0;
}

h1 {
  font-family: 'Changa One', sans-serif;
  margin: 15px 0;
  font-size: 1.75em;
  font-weight: normal;
  line-height: 0.8em;
}

h2 {
  font-size: 0.75em;
  margin: -5px 0 0;
  font-weight: normal;
}



/***********************
NAVIGATION
***********************/

nav {
  text-align: center;
  padding-bottom: 10px 0;
  margin: 20px 0 0;
}

nav ul {
  list-style: none;
  margin: 0 10px;
  padding: 0;
  }

nav li {
  display: inline-block;
}

nav a {
  font-weight: 800;
  padding: 15px 10px;
}

/***********************
FOOTER
***********************/

footer {
  font-size: 0.75em;
  text-align: center;
  clear: both;
  padding-top: 50px;
  color: #ccc;
}

.social-icon {
  width: 20px;
  height: 20px;
  margin: 0 5px;
}



/***********************
PAGE: PORTFOLIO
***********************/

#gallery {
  margin: 0;
  padding: 0;
  list-style: none;
}

#gallery li {
  float: left;
  width: 45%;
  margin: 2.5%;
  background-color: #f5f5f5;
  color: #bdc3c7  
  }

#gallery li a p{
  margin: 0;
  padding: 5%;
  font-size: 0.75em;
  color: #bdc3c7  
}




/***********************
PAGE: ABOUT
***********************/

.profile-photo {
  display: block;
  margin: 0 auto 30px;
  max-width: 150px;
  border-radius: 100%;
}



/***********************
CONTACT
***********************/

.contact-info {
  list-style: none;
  padding: 0;
  margin: 0;
  font-size: 0.9em;
}

.contact-info a{
  display: block;
  min-height: 20 px;
  background-repeat: no-repeat;
  background-size: 20px 20px;
  padding: 0 0 0 30px;
  margin: 0 0 10px;
}

.contact-info li.phone a {
  background-image: url('../img/phone.png')
}

.contact-info li.mail a {
  background-image: url('../img/mail.png')
}

.contact-info li.twitter a {
  background-image: url('../img/twitter.png')
}

/***********************
COLORS
***********************/


/* site body*/
body {
background-color: #fff;
  color: #999;
}

/* green header */
header {
  background: #6ab47b; 
  border-color: #599a68;
}

/* logo text */
h1, h2 {
  color: #fff; 
}

/* links */
a {
  color: #6ab47b;
}

/* nav background on mobile */
nav {
  background: #599a68;
}

/* navlink */
nav a, nav a:visited {
 color: #fff;
}

/* selected nav link */
nav a.selected, nav a:hover {
  color: #32673f;
}






</p>