title: d3 arrows in Force Directed Graph
body: <p>I am puzzled. Why by simply copying and pasting the example <a href="http://bl.ocks.org/1153292" rel="nofollow noreferrer">http://bl.ocks.org/1153292</a> the arrows do not align. (see below)</p>
  
  <p><img src="https://i.stack.imgur.com/MvRer.png" alt="enter image description here"></p>
  
  <p>UPDATE: it works in chrome and safai but not in Firefox... even more puzzled. Any ideas?</p>
  
  <p>What would you change in the example to get straight lines instead of curves?</p>
  
  <p>Thanks.</p>