[sunfighter]

Using position: fixed; is correct, but it is better to place the fixed object using top/bottom and left/right selectors.
Your margin-left:850px; really makes a lot of empty space if it was followed.
Try this (I have commented out what you don't need):

.sidenav{
	//margin-top:10px;
	//margin-right:10px;
	//margin-left:850px;
	//float:right;
	position: fixed;
	top: 10px;
	right: 10px;
	width:175px;
....