Try this. i think this is what you want to do.
<html>
<head>
<style type="text/css">
#menu {
position: fixed;
left: 0;
top: 50%;
width: 8em;
margin: -2.5em 0 0 0;
z-index: 5;
background: hsla(80, 90%, 40%, 0.7);
color: white;
border: solid hsla(80, 90%, 40%, 0.5);
box-shadow: 0 1px 3px black;
border-radius: 0.5em 3em 3em 0.5em;
}
#menu li { margin: 0 }
#menu a { color: inherit }
#menu { position: absolute }
*>#menu { position: fixed }
</style>
</head>
<body>
<ul id="menu">
<li><a href="#">Section 1</a>
<li><a href="#">Section 2</a>
<li><a href="#">Section 3</a>
</li></li></li></ul>
<h1 style="background: hsla(12, 20%, 20%, 0.7); color:white">Scroll Down Yaar!! :-)</h1><br /><br /><br /><br /><br /><br />
<h1 style="background: hsla(212, 20%, 20%, 0.7); color:white">Scroll Down Yaar!! :-)</h1><br /><br /><br /><br /><br /><br />
<h1 style="background: hsla(121, 40%, 20%, 0.7); color:white">Scroll Down Yaar!! :-)</h1><br /><br /><br /><br /><br /><br />
<h1 style="background: hsla(12, 20%, 20%, 0.7); color:white">Scroll Down Yaar!! :-)</h1><br /><br /><br /><br /><br /><br />
<h1 style="background: hsla(212, 20%, 20%, 0.7); color:white">Scroll Down Yaar!! :-)</h1><br /><br /><br /><br /><br /><br />
<h1 style="background: hsla(121, 40%, 20%, 0.7); color:white">Scroll Down Yaar!! :-)</h1><br /><br /><br /><br /><br /><br />
</body>
</html>