Rightmost Nav Element falls to second line after the media query at 660px.

/******************************
GENERAL
******************************/

html { 
    overflow-y: scroll; 
}

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

#wrapper{
  max-width: 940px; /* max width is no larger than max. */
  margin: 0 auto; /* the first is top and bottom and the second is left and right */
  padding: 0 5%; /* 5% of parrent element width */
}

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: 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 18px;
}



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

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

.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;
  max-width: 150px;
  margin: 0 auto 30px;
  border-radius: 100%;
  clear: both;
}




/******************************
PAGE: CONTACT
******************************/

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

.contact-info a {
  display: block;
  min-height: 20px;
  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.email 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;
}

/* Mobile nav background */
nav {
  background: #599a68;
}

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

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

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

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

@media screen and (min-width: 480px){
  /******************************
  TWO COLUMN LAYOUT
  ******************************/

  #primary{
    width: 50%;
    float: left;
  }

  #secondary{
    width: 40%;
    float: right;
  }



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

  #gallery li{
    width: 28.3333%;
  }

  #gallery li:nth-child(4n){
    clear: left;
  }



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

  .profile-photo {
    float: left;
    margin: 0 5% 80px 0;
  }
}

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

  /******************************
  HEADER
  ******************************/
  nav{
    background: none;
    float: right;
    font-size: 1.125em;
    margin-right: 5%;
    text-align:right;
    width: 52%;
  }

  #logo {
    float: left;
    margin-left: 5%;
    text-align:left;
    width: 35%;

  }

}