title: Sticky menu with options marked
body: <p>I'm having many problems with an idea I'm trying to do. I have a web with an smooth vertical scrolling and I need a menu on the left which marks in which section I am.</p>
  
  <p>So the ideal thing would be to make this menu change depending on the point I pass by the scrollbar. Please some of you has any idea?</p>
  
  <p>I've already got to make this menu appears in an specific point of the scrollball cause at first I dont want any menu at all.</p>
  
  <p>THANKS!</p>