code:
#menu a{
width: 50px;
height: 15px;
display: block;
background: #011F9E;
color: white;
float: left;
}
#menu a:hover{
background: #E1E1FF;
border-left: 3px solid #011F9E;
}
In bold is the bit you need to add to make them all on one line, and i also deleted the stuff you dont need in the :hover statement because it should be inherited from the previous bit.