Set text based on Form <select> value
<p>I have the following <code>&lt;select&gt;</code> in a form:</p>

<pre><code>&lt;select style="width: 100px; text-align: center;"&gt;
  &lt;option value="email"&gt;Email&lt;/option&gt;
  &lt;option value="telephone"&gt;Phone&lt;/option&gt;
&lt;/select&gt;
</code></pre>

<p>The default option is <code>Email</code> so the following <code>&lt;input&gt;</code> is show:</p>

<pre><code>&lt;p class="email_form"&gt;Please supply your Email Address&lt;/p&gt;
&lt;input onfocus="if(!this._haschanged){this.value=''};this._haschanged=true;" style="width: 270px" type="email" name="email" id="email" value="jose.gonzalez@hotmail.com"&gt;
</code></pre>

<p>However if they choose <code>telephone</code> I want to change the above  to ask for a telephone number?</p>
