Missing something in my HTML for my responsive columns in contact page

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

a {
 text-decoration: none; 
}

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

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

}

a {
  color:#6ab47b;
}

img {
 max-width:100%; 
}

h3 {

 margin:0 0 1em 0;

}

    /*********
  BODY
********/

  body {
 background-color:#fff;
  color:#999;
}


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

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

}

h1 {
   font-family: 'Fjalla One', sans-serif;
    margin: 15px 0;
    font-size: 1.75em;
  }

header {
  background: #6ab47b;
  border-color: #599a68;

}

h1, h2 {
  color:  #fff;

}

nav {

  background: #599a68;
}

nav a.selected {
 color: #32673f; 
}

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


}

nav a, nav a:visited{
  color: #fff; 
}

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

}

nav li {
  padding: 0 5px;
 display:inline-block; 

}

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

}

.social-icon{
  width: 32px;
  height: 32px;
  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%;

}

  /*********
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.mail a {
 background-image:url('../img/mail.png'); 

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

}