body{
  margin: 0;
 font-family: helvetica, Arial, sans-serif;
 font-size: 1.2rem;
}
.wrapper{
  max-width: 960px;
   margin:0 auto;
}
header, footer{
  height: 160px;
  background: silver;
  clear: both; /* stopt das floating */
} 
#hauptbereich, #seitenbereich{
  min-height: 500px;
  background: #acacac;
}
#hauptbereich{
  width: 60%;
  float: left;
}
#seitenbereich{
  width: 30%;
  float: right;
}
/*navigation*/
nav {
  margin: 20px 0;
}
nav ul{
  margin: 0;
  padding: 0;
  list-style-type: none;
}
nav li{
  display: inline;
}
nav li a{
  margin: 0 20px 0 0;
  text-decoration: none;
  padding: 10px 8px;
  border-top-left-radius: 10px;
  border-bottom-right-radius: 10px;
}
nav li a:link, nav li a:visited{
  background-color: coral;
  color: #000;
}
nav li a:hover{
  background-color: #5c5c5c;
  color: #fff;
}