Form.disable disables all elements in a form. Prototype does this by setting an element’s ‘disabled’ property to ‘true’. See Form.enable
Form.disable('test');
<form id="test" method="post">
Number
<select name="guest[size]">
<option value="0">0</option>
<option value="1" selected>1</option>
<option value="2">2</option>
</select>
<br/>
<label for="text">Text</label>
<input id="form_text" name="form[text]" size="30" type="text" value="" /><br/>
<label for="form_radio">Radio</label>
<input id="form_radio_yes" name="form[radio]" size="30" type="radio" value="1" />yes
<input id="form_radio_no" name="form[radio]" size="30" type="radio" value="0" />no
<br/>
</form>
<p>
<a href="#" onClick="Form.disable('test');">disable</a>
<a href="#" onClick="Form.enable('test');">enable</a>
</p>
Creates: