title: jQuery $("#field") is null?
body: <p>I have a selectbox with month periods in it. </p>
  
  <p>Here is my code: </p>
  
  <pre><code>$(function(){ 
                          $("#ppsub_ppterm_id").change(function(){ 
                                          var term = this.options[this.selectedIndex].text; 
                                          if(term == "Eenmalig"){ 
                                                  $(".idealtd").show(); 
                                          }else{ 
                                                  $(".idealtd").hide(); 
                                                  //$("#ppsub_amount option:selected").val('anders'); 
                                          } 
                          }); 
          }); 
  &lt;select name="ppsub_ppterm_id" class="ppsub_ppterm_id" 
  id="ppsub_ppterm_id" style="width: 100px; font-size: 11px;"&gt; 
                                                  &lt;option value="M"&gt;Maand&lt;/option&gt; 
                                                  &lt;option value="K"&gt;Kwartaal&lt;/option&gt; 
                                                  &lt;option value="H"&gt;Halfjaar&lt;/option&gt; 
                                                  &lt;option value="J"&gt;Jaar&lt;/option&gt; 
                                                  &lt;option selected value="E"&gt;Eenmalig&lt;/option&gt; 
                                          &lt;/select&gt; 
  </code></pre>
  
  <p>But when i load my page i staight away get an error: </p>
  
  <p>$("#ppsub_ppterm_id") is null </p>
  
  <p>Line 17 </p>
  
  <p>Any ideas?</p>