title: Web2py: Custom CSS class for custom form
body: <p>How do i specify the class of a custom web2py form?
  for e.g.</p>
  
  <pre><code>{{=form.custom.begin}}
  Image name: &lt;div&gt;{{=form.custom.widget.name}}&lt;/div&gt;
  Image file: &lt;div&gt;{{=form.custom.widget.file}}&lt;/div&gt;
  Click here to upload: {{=form.custom.submit}}
  {{=form.custom.end}}
  </code></pre>
  
  <p>How do i specify the CSS class for <code>form</code> ?</p>