title: Check if a value has been updated on a html page
body: <p>I have the following two forms. Is there a way of detecting when the value of the forms changes, preferably logging the value before and after, and if so what function actually changes the value.</p>
  
  <pre><code>&lt;div class="chkField"&gt;
    &lt;label for="billing_state"&gt;[CustomerInfo_state]&lt;/label&gt;
    &lt;select id="billing_state" onchange="check_address('billing');" name="billing_state" tabindex="9" class="txtBoxStyle"&gt;
    &lt;/select&gt;
    &lt;!--START: req_billing_state--&gt; 
    &lt;img src="assets/templates/common/images/error2.gif" width="12" height="12" alt="" /&gt; 
    &lt;!--END: req_billing_state--&gt;
    &lt;div class="clear"&gt;&lt;/div&gt;
  &lt;/div&gt;
  
  &lt;div class="chkField"&gt;
    &lt;label for="billing_zip"&gt;[CustomerInfo_zip]&lt;/label&gt;
    &lt;input name="billing_zip" maxlength="15" type="text" id="billing_zip" value="[billing_zip]" size="10" tabindex="10" class="txtBoxStyle" onchange="clearContent(this);check_address('billing');" /&gt;
    &lt;!--START: req_billing_zip--&gt; 
    &lt;img src="assets/templates/common/images/error2.gif" width="12" height="12" alt="" /&gt; 
    &lt;!--END: req_billing_zip--&gt;
    &lt;div class="clear"&gt;&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>