When I test my code that is below only the Trademark Owner selection works. I haven't posted all of my code as there are lots of it. Can someone please have a look at my code and tell me why the other options aren't working? Thanks in advance.

Code JavaScript:
	function dropdown1() {
	var a = document.getElementById('eligibilitytype').value;
	// textboxes, etc
	var regidtype1 = document.getElementById('regidtype1');
	var regidno1 = document.getElementById('regidno1');
	var regidno2 = document.getElementById('regidno2');
	var eligidtype2 = document.getElementById('eligidtype2');
	var eligname1 = document.getElementById('eligname1');
	var eligidno2 = document.getElementById('eligidno2');
	var eligname2 = document.getElementById('eligname2');
	// classes
	var regidtype2 = document.getElementById('regidtype2');
	var regidno = document.getElementById('regidno');
	var eligidtype1 = document.getElementById('eligidtype1');
	var eligidno1 = document.getElementById('eligidno1');
	var eligidname1 = document.getElementById('eligidname1');
	var abnacn = document.getElementById('abnacn');
	var assocno = document.getElementById('assocno');
	var abnacnbn = document.getElementById('abnacnbn');
	var tradename = document.getElementById('tradename');
	var tradeno = document.getElementById('tradeno');
    if (a == "Company") {
		// for company
		regidtype2.style.visibility = "visible";
		regidno.style.visibility = "visible";
		abnacn.style.visibility = "visible";
		regidtype1.style.visibility = "visible";
		regidno1.style.visibility = "visible";
		// for other combo box options
		assocno.style.visibility = "hidden";
		regidno2.style.visibility = "hidden";
		eligidtype2.style.visibility = "hidden";
		eligidno1.style.visibility = "hidden";
		abnacnbn.style.visibility = "hidden";
		eligidtype1.style.visibility = "hidden";
		eligidno1.style.visibility = "hidden";
		eligname1.style.visibility = "hidden";
		tradename.style.visibility = "hidden";
		eligname1.style.visibility = "hidden";
		eligidno2.style.visibility = "hidden";
		tradeno.style.visibility = "hidden";
		tradename.style.visibility = "hidden";
		eligname2.style.visibility = "hidden";
    } else {
		// for company
		regidtype2.style.visibility = "hidden";
		regidno.style.visibility = "hidden";
		abnacn.style.visibility = "hidden";
		regidtype1.style.visibility = "hidden";
		regidno1.style.visibility = "hidden";
		// for other combo box options
		assocno.style.visibility = "hidden";
		regidno2.style.visibility = "hidden";
		eligidtype2.style.visibility = "hidden";
		eligidno1.style.visibility = "hidden";
		abnacnbn.style.visibility = "hidden";
		eligidtype1.style.visibility = "hidden";
		eligidno1.style.visibility = "hidden";
		eligname1.style.visibility = "hidden";
		tradename.style.visibility = "hidden";
		eligname1.style.visibility = "hidden";
		eligidno2.style.visibility = "hidden";
		tradeno.style.visibility = "hidden";
		tradename.style.visibility = "hidden";
		eligname2.style.visibility = "hidden";
    }

Code:
<select name="eligibilitytype" id="eligibilitytype" onchange="dropdown1();">
            <option value="none" selected="selected">-- Please select --</option>
            <option value="Commercial Statutory Body">Commercial Statutory Body</option>
            <option value="Company">Company</option>
            <option value="Incorporated Association">Incorporated Association</option>
            <option value="Partnership">Partnership</option>
            <option value="Pending TM Owner">Pending TM Owner</option>
            <option value="Registered Business">Registered Business</option>
            <option value="Sole Trader">Sole Trader</option>
            <option value="Trademark Owner">Trademark Owner</option>
          </select>
<div class="regidtype2" id="regidtype2">Registrant ID Type:</div><br />
<div class="regidno" id="regidno">Registrant ID Number:</div><br />
<div class="eligidtype1" id="eligidtype1">Eligibility ID Type:</div><br />
<div class="eligidno1" id="eligidno1">Eligibility ID Number:</div><br />
<div class="eligidname1" id="eligidname1">Eligibility ID Name:</div>
<select name="regidtype1" id="regidtype1" style="visibility: hidden" >
            <option value="ABN" selected="selected">ABN</option>
            <option value="ACN">ACN</option>
          </select>
          <br />
<input name="regidno1" id="regidno1" type="text" style="visibility: hidden" /> <span class="abnacn" id="abnacn">(ABN / ACN)</span>
<input name="regidno2" id="regidno2" type="text" style="visibility: hidden" /> <span class="assocno" id="assocno">(Association Number)</span>
<select name="eligidtype2" id="eligidtype2" style="visibility: hidden">
  <option value="ABN">ABN</option>
  <option value="ACN">ACN</option>
  <option value="ACT BN">ACT BN</option>
  <option value="NSW BN">NSW BN</option>
  <option value="NT BN">NT BN</option>
  <option value="QLD BN">QLD BN</option>
  <option value="SA BN">SA BN</option>
  <option value="TAS BN">TAS BN</option>
  <option value="VIC BN">VIC BN</option>
  <option value="WA BN">WA BN</option>
</select><br />
<input name="eligidno1" id="eligidno1" type="text" style="visibility: hidden" /> <span class="abnacnbn" id="abnacnbn">(ABN / ACN / BN)</span>
<input name="eligname1" id="eligname1" type="text" style="visibility: hidden" /> <span class="tradename" id="tradename">(Trademark Name)</span>
<input name="eligidno2" id="eligidno2" type="text" style="visibility: hidden" /> <span class="tradeno" id="tradeno">(Trademark Number)</span><br />
<input name="eligname2" id="eligname2" type="text" style="visibility: hidden" />