[Excavator]

Hello GedC,
Your ul that flys out covers that right 40px or so on the parent.

When you use absolute positioning on your flyout ul, you need to use positioning instead of margin.

Look at these changes to your CSS -

#nav li {
	list-style : none;
	/*width : 150px;
	display : block;  --li is already block level*/
  position: relative;
}
 
#nav li a{
	display : block;
	text-decoration : none;
	background : #036;
	padding-left : 8px;
	line-height : 29px;
	color : #fff;
	border-bottom : solid 1px #fff;
	width : 150px;
}

#nav li ul {
  padding: 0;
	display : none;
}

#nav li:hover ul{
	display : block;
	position : absolute;
  top: 0;
 left: 158px;
	/*margin-top : -30px;
	margin-left : 110px;*/
}