Question

I’m using Ajax with JQuery. I am sending data with ajax to return.php(for example)..
When ajax sending data, i want to write to screen “loading..”.

Answer 1

A nice place to get the animation would be here

Then indeed, like @royinamir said, show/hide the animation.
Give the animation an ID. Short example (using jQuery):

<div id="laoding">
<p>Loading data</p>
</div>

in the CSS:

#loading{
  display: none;
  background: url(images/icon_loading_ani.gif) no-repeat;//the url of your animated gif
  background-position: 0px center;
  min-height: 35px;
  padding: 5px 0 0 0;
}

and in jQuery:

$.ajax({
        type: 'get',
        url: url,
        data: 'ajax=1,
        beforeSend: function () {
            $('#get_data').show();
        },
        success: function (data) {
            $('#filter').show();
// do some other stuff
        }
    });