I have the following script to check for the first child element of each div with the class 'tabSection'.

var tabContain = document.getElementById ('tabContain');
var tabBox = document.getElementById ('tabBox');
        
// determine amount of tabs
// get number of sections
var j = 0;
var section = new Array ();
for (i = 0; i < tabBox.childNodes.length; i ++)
    {
        if (tabBox.childNodes[i].className == 'tabSection')
            {
                section[j] = tabBox.childNodes[i];
                j ++;
            }
    }

alert (section[0].childNodes.length);
for (i = 0; i < section.length; i ++)
    {
        alert (section[i].firstChild.nodeName);
    }

    <h1>Tab Generator
    </h1>
    <div id="tabContain">
      <div id="tabBox" style="border:#444 solid 1px">
        <div class="tabSection">
          <h2>div one</h2>
          <p>Content for New Div Tag Goes Here</p>
        </div>
        <div class="tabSection">
          <h2>div two</h2>
          <p>Content for New Div Tag Goes Here</p>
        </div>
        <div class="tabSection">
          <h2>div three</h2>
          <p>Content for New Div Tag Goes Here</p>
        </div>
      </div>
    </div>
<script type="text/javascript" src="tab.js"></script>
<script type="text/javascript">
tabBoxHeight ('200px');
</script>

However the alerts at the end show that each div appears to have 5 child elements (when I expected 4). It also states that the nodeName of each firstChild is '#text', when I would expect it to be a heading tag.

Does anyone know what code I should be using to access the heading of each div? At the moment I'm using 'section[i].firstChild' but with no success!

It comes down to this:
Because you have your HTML formatted neatly, there is some whitespace between the <div> and <h2>, which accounts for the #text you are finding.

Just loop the childNodes again and for each, just check the tagName.

for (i = 0; i < section.length; i ++)
    {
        for(name in section[i].childNodes){
              if(section[i].childNodes[name].tagName == 'H2'){
                      // do your stuffs here
                      // but don't forget to break :P
                      break;
              }
        }
    }

Thanks! That's solved a lot of confusion