I will highlight what I added/changed in your code. If any questions just ask.
@charset "UTF-8";
#nav {
font-family: Arial, Helvetica, sans-serif;
position: relative;
width:100%;
height: 35px;
font-size: 14px;
font-color: #090;
background-color: #33C;
clear: both;
float: none;
margin-top: 120px;
}
/*margin-top: 150px;
margin-right: 0px;
margin-bottom: 0px;
margin-left: 0px;
padding: 0px;
}*/
#nav ul {
list-style-type: none;
position: absolute;
margin-bottom: 0px;
margin-top: 0px;
line-height: 0px;
}
#nav ul li {
float: left;
position: relative;
background-color: #F00;
height: 15px;
margin-right: 0px;
margin-left: 100px;
padding-top: 10px;
width: 75px;
margin-top: 5px;
}
#nav ul li a {
text-align: center;
text-decoration: none;
display: block;
color:#fff;
padding: 1px;
/*float: none;
clear: none;
white-space: nowrap;*/
}
#nav ul li ul {
display: none;
/*white-space: normal;
margin: 0px;*/
}
#nav ul li:hover ul {
display: block;
position: relative;
left:-90px;
top:8px;
background-color: #0F0;
margin-top:0px;
margin:bottom:0px;
padding:0;
/*padding: 0px;
margin-top: 20px;
margin-right: 0px;
margin-bottom: 0px;
margin-left: 0px;*/
}
#nav ul li ul li {margin-top: 0px;}
#nav ul li: hover ul li a {
display: block;
width: 200px;
text-align:center;
margin:0;padding:0;
/*font-size: 14px;*/
}
#nav ul li: hover ul li a:hover{
margin-left: 0px;
padding-left: 0px;
}