One line form

ck_form.css

.ck_form.single_line {
	background: #f9f9f9;
	font-family: 'Helvetica Neue', Helvetica, Arial, Verdana, sans-serif;
	line-height: 1.5em;
	overflow: hidden;
	color: #666;
	font-size: 16px;
	border: solid 1px #d1d1d1;
	-webkit-box-shadow: none;
	-moz-box-shadow: none;
	box-shadow: none;
	clear: both;
	margin: 20px 0px;
	text-align: center;
}


.ck_form.single_line h3, #content .ck_form.single_line h3 { 
	text-align: center; 
	margin: 0px 0px 10px; 
	font-size: 28px;
}

.ck_form.single_line h4, #content .ck_form.single_line h4 { 
	text-align: center; 
	font-family: 'Open Sans', Helvetica, Arial, sans-serif;	
	text-transform: uppercase;
	font-size: 18px;
	font-weight: normal;
	padding-top: 0px;
	margin-top: 0px;
}

.ck_form.single_line p {
	padding: 0px;
}

.ck_form * {
	-webkit-box-sizing: border-box;
	-moz-box-sizing: border-box;
	box-sizing: border-box;
}

#ck_subscribe_form {
  clear: both;
}

.ck_form.single_line .ck_form_fields {
	width: 100%;
	float: left;
	padding: 5%;
}
/* Form fields */

.ck_errorArea {
	display: none; /* temporary */
}

#ck_success_msg {
	padding: 10px 10px 0px;
	border: solid 1px #ddd;
	background: #eee;
}

.ck_form.single_line input[type="text"], .ck_form.single_line input[type="email"] {
	font-size: 18px;
	padding: 10px 8px;
	width: 68%;
	border: 1px solid #d6d6d6; /* stroke */
	-moz-border-radius: 3px;
	-webkit-border-radius: 3px;
	border-radius: 3px; /* border radius */
	background-color: #fff; /* layer fill content */
	margin-bottom: 5px;
	height: auto;
	float: left;
	margin: 0px;
	margin-right: 2%;
	height: 42px;
}

.ck_form input[type="text"]:focus, .ck_form input[type="email"]:focus {
	outline: none;
	border-color: #aaa;
} 

.ck_form.single_line .ck_checkbox {
  display: none;
}

.ck_form.single_line .ck_subscribe_button {
    color: #fff;
    margin: 0px;
    padding:  11px 0px;
    font-size: 18px;
    background: #0d6db8;
    -moz-border-radius: 3px;
    -webkit-border-radius: 3px;
    border-radius: 3px; /* border radius */
    cursor: pointer;
    border: none;
    text-shadow: none;
    width: 30%;
    float: left;
    height: 42px;
  }
  
  
.ck_form.single_line .ck_guarantee {
	color: #626262;
	font-size: 15px;
	text-align: center;
	padding: 15px 0px 0px;
	display: block;
	clear: both;
}

ck_form.html

<script src="https://app.convertkit.com/assets/CKJS4.js?v=18"></script>
<div class="ck_form single_line">

  <div class="ck_form_fields">
  
  	<h3>Never miss an essay</h3>
  	<h4>Join the free newsletter</h4>

    <div id='ck_success_msg'  style='display:none;'>
      <p>You’re Almost Done! I just sent you an email. Open it and confirm your email address by clicking the link in it. You won't be subscribed until you complete this step.</p>
    </div>

    <!--  Form starts here  -->
    <form id="ck_subscribe_form" class="ck_subscribe_form" action="https://app.convertkit.com/landing_pages/000/subscribe" data-remote="true">
      <input type="hidden" name="id" value="000" id="landing_page_id"></input>
      <div class="ck_errorArea">
        <div id="ck_error_msg" style="display:none">
          <p>There was an error submitting your subscription. Please try again.</p>
        </div>
      </div>
          <label class="ck_label" for="ck_emailField" style="display:none">Email Address</label>
        
          <input type="email" name="email" placeholder="Email address" class="ck_email_address" id="ck_emailField" required></input>

	      <button class="subscribe_button ck_subscribe_button btn fields" id='ck_subscribe_button'>
	        Subscribe
	      </button>
      <span class="ck_guarantee">No spam guaranteed. Unsubscribe at any time.</span>
    </form>
  </div>
 </div>