выпадающее меню 100%

html,
body {
margin: 0;
padding: 0;
}

body {
width: 380px;
min-height: 280px;
padding: 10px;

font-size: 14px;
line-height: 1.4;
font-family: “Arial”, sans-serif;

background-color: #ecf0f1;
}

.main-menu {
position: relative;
margin: 0;
padding: 0;
list-style: none;
}

.main-menu a {
display: block;
padding: 10px 15px;
width: 170px;

color: #fff;
background-color: #2980b9;
text-decoration: none;
border-bottom: 2px solid #2c3e50;
}

.main-menu > .open > a {
background-color: #1abc9c;
}

.main-menu .sub-menu {
position: absolute;
top: 41px;
left: 180px;
z-index: 2;
list-style: none;
padding: 0;
}

.main-menu .sub-menu a {
background-color: #1abc9c;
border-bottom: 2px solid #2ecc71;
}