body {
  text-align:center;
  font-family: Verdana;
}

ul {
  list-style-type: none;
}

h1 {
  font-size: large;
}

#content {
  width: 680px; 
  margin: 0 auto;
  text-align: justify;
  padding: 15px;
}

#nav-menu{
  width: 680px;
  overflow: hidden;
  margin: 0 auto;
  border-bottom: 1px solid black; /*bottom horizontal line that runs beneath tabs*/
}

#nav-menu ul{
  margin: 0;
  padding: 0;
  padding-left: 10px; /*offset of tabs relative to browser left edge*/
  font: bold 12px Verdana;
}

#nav-menu li{
  display: inline;
  margin: 0;
}

#nav-menu li a{
  float: left;
  display: block;
  text-decoration: none;
  margin: 0;
  padding: 7px 8px; /*padding inside each tab*/
  border-right: 1px solid white; /*right divider between tabs*/
  color: white;
  background: #414141; /*background of tabs (default state)*/
}

#nav-menu li a:visited{
  color: white;
}

#nav-menu li a:hover, #nav-menu li.selected a{
  background: black; /*background of tabs for hover state, plus tab with "selected" class assigned to its LI */
}