How make a slide down form with bootstrap

Are you talking about a modal?  http://getbootstrap.com/javascript/#modals

Modals are chunks of html that are hidden until accessed.  Then instead of a pop up or alert, they appear with or without animation.  They can close in the same way.  You can even populate the modal via ajax.  If I am doing a log in form, this is probably what I would use to have something appear when logged out, then "slide down" when the log in button is pressed and the log in works.

<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal" data-whatever="@mdo">Open modal for @mdo</button>
<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal" data-whatever="@fat">Open modal for @fat</button>
<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal" data-whatever="@getbootstrap">Open modal for @getbootstrap</button>
...more buttons...

<div class="modal fade" id="exampleModal" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true">
  <div class="modal-dialog">
    <div class="modal-content">
      <div class="modal-header">
        <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">&times;</span></button>
        <h4 class="modal-title" id="exampleModalLabel">New message</h4>
      </div>
      <div class="modal-body">
        <form>
          <div class="form-group">
            <label for="recipient-name" class="control-label">Recipient:</label>
            <input type="text" class="form-control" id="recipient-name">
          </div>
          <div class="form-group">
            <label for="message-text" class="control-label">Message:</label>
            <textarea class="form-control" id="message-text"></textarea>
          </div>
        </form>
      </div>
      <div class="modal-footer">
        <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
        <button type="button" class="btn btn-primary">Send message</button>
      </div>
    </div>
  </div>
</div>

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I am making a phone application and I don't want to have  a popup dialog..  

What I have in a search result screen  and a filter button in the nav bar. When the button is press, I would like the current content to slide down on page and be disable and the filter screen to be on the top page . The user then make some choices and submit. Then they are back to the original screen with the new results

Thanks you for the sample and link.. . I will have  a look

Thanks for your help..  I will try the modal approach