old_contents: // create div
  var sievehelpdiv = d3.select(".title").append("div")
  	.attr("id", "sievehelpdiv")
  	.classed("hidden", true);
  
  // add div content
  sievehelpdiv.append("h1").text("This is a big title!");
  
  // hit window is the 'help' text
  // set its behavior for mouseover and mouseout
  d3.select(".sievehelplink")
  	.on("mouseover", function() {sievehelpdiv.classed("hidden", false);})
  	.on("mouseout", function() {sievehelpdiv.classed("hidden", true);});
new_contents: // create div
  var sievehelpdiv = d3.select(".title").append("div")
  	.attr("id", "sievehelpdiv")
  	.classed("hidden", true);
  
  // add div content
  sievehelpdiv.append("h1").text("How to use this tool");
  sievehelpdiv.append("p").text("Select sites in the shaded area.");
  
  // hit window is the 'help' text
  // set its behavior for mouseover and mouseout
  d3.select(".sievehelplink")
  	.on("mouseover", function() {sievehelpdiv.classed("hidden", false);})
  	.on("mouseout", function() {sievehelpdiv.classed("hidden", true);});
subject: Add slightly more relevant content to the help div