There is a small gap after the navigation - html

Question

I have a navigation bar which is OK, but just underneath that there is a 1px line that I cannot get rid of, it should be flush with the address underneath. This is the code that I have can anyone suggest anything?
There is also some of the html which was so hard formatting on here anyhow they want me to add more text. So it is the address underneath the naviation
address.space {
width: 100%;
background: #FF9900;
font-family: 'Monserrat', sans-serif;
text-align: center;
display: inline-block;
font-size: 1em;
margin-bottom: 20px;
}
/*menu*/
.nav {
background-color: #3333FF;
width: 100%;
height: 40px;
line-height: 40px;
}
.menu {
font-family: Monserrat, sans-serif;
font-size: 20px;
color: white;
list-style-type: none;
padding: 0;
position: relative;
z-index: 1;
}
.menu a {
text-decoration: none;
color: #fff;
line-height: 40px;
height: 40px;
display: block;
}
.menu ul li {
text-align: center;
display: inline-block;
padding: 0 20px 0 20px;
width: 13.5%;
height: 40px;
}
.menu li:visited,
.menu li:active,
.active,
.menu li:hover {
background: #0000EE;
color: #fff;
}
label {
margin: 0 14px 0 0;
font-size: 20px;
display: none;
}
#toggle {
display: none;
}
#media only screen and (max-width: 500px) {
html,
body,
#main,
#firstside,
.firstsidewider,
#second,
.wide {
width: 100%;
font-size: 1em;
}
h1 span {
display: none;
}
label {
cursor: pointer;
display: block;
color: #fff;
}
.menu {
text-align: center;
width: 100%;
display: none;
}
.menu li a {
border-bottom: 1px solid #F4F4F4;
display: block;
background: #3333FF;
margin: -20px;
padding: 0;
}
.active,
.menu li:hover {
color: #fff;
background: 0;
}
#toggle:checked+.menu {
display: block;
}
<header id="banner">
<div class="nav">
<label for="toggle">☰</label><input id="toggle" type="checkbox">
<div class="menu">
<ul>
<li>Home</li>
<li>News</li>
<li>Contacts
</li>
<li>Members
</li>
<li>Policies
</li>
<li>Links</li>
<li class="active">
Volunteer/li>
</ul>
</div>
</div>
<address class="space">
Meeting Address: YMCA -The Lecture Room 29 Rush Green
Road
4.00pm - 6.00pm</address>
<section id="leftheader">
<h1>Hubb <span>support group</span></h1>