make selection before ghost selection

D3.md

@@ -65,7 +65,7 @@ d3.text('path', function(error, data){});
 ## Data binding
 
 ```javascript
-d3.selectAll('circle')//make a "ghost call" to all circles, even if there are none already
+d3.select('svg').selectAll('circle')//make a "ghost call" to all circles, even if there are none already.  Make sure to select the svg, or appended circles will attach to html element
 	.data(dataArray) //joins each element in dataArray to an element in the selection
 	.enter() //returns the sub section of dataArray that has not been matched with DOM elements
 	.append('circle'); //creates a DOM element for each of the remaining dataArray elements