title: Does InsertMode.Replace replace the content or the whole element?
body: <p>In MVC 3, there is an option to specify the type of replacement when using <code>Ajax.BeginForm</code>. Does it replace the content of the element that you specify in <code>UpdateTargetId</code> or the element as a whole?</p>
  
  <pre><code>        @using (Ajax.BeginForm("action", "controller", new AjaxOptions
          {
                      UpdateTargetId = "TargetElementId",
                      HttpMethod = "POST",
                      InsertionMode = InsertionMode.Replace,
                  }, new { @id = "FormId"  }))
          {
          }
  </code></pre>