.content_tab{
position:relative; 
left:10px; 
top:-5px; 
width:680px; 
z-index:3;
}
.content_tab_home{
position:relative; 
left:10px; 
top:-5px; 
width:390px; 
z-index:3;
}
.referenz_linie{
position:relative; 
left:0px; 
top:-2; 
width:680px; 
height:1px;
}