title: Show input field only if a specific option is selected
body: <p>I'm trying to make a form which checks if a certain option is selected from a "select" tag. Here is my current HTML:</p>
  
  <pre><code>&lt;select onchange="yesnoCheck()"&gt;
      &lt;option id="noCheck" value=""&gt;Valitse automerkkisi&lt;/option&gt;
      &lt;option id="noCheck" value="lada"&gt;Lada&lt;/option&gt;
      &lt;option id="noCheck" value="mosse"&gt;Mosse&lt;/option&gt;
      &lt;option id="noCheck" value="volga"&gt;Volga&lt;/option&gt;
      &lt;option id="noCheck" value="vartburg"&gt;Vartburg&lt;/option&gt;
      &lt;option id="yesCheck" value="other"&gt;Muu&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>This is the div element which should become visible after "Muu" is selected:</p>
  
  <pre><code>&lt;div id="ifYes" style="display: none;"&gt;
      &lt;label for="car"&gt;Muu, mikä?&lt;/label&gt; &lt;input type="text" id="car" name="car" /&gt;&lt;br /&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>And here is the JavaScript I'm trying to use:</p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
      function yesnoCheck() {
          if (document.getElementById("yesCheck").checked) {
              document.getElementById("ifYes").style.display = "block";
          } else {
              document.getElementById("ifYes").style.display = "none";
          }
      }
  &lt;/script&gt;
  </code></pre>
  
  <p>But it's not working...</p>