I have just noticed that every page with datepicker shows a thin bar at the bottom.  Firebug shows it is the following div

 

<div class="ui-datepicker ui-widget ui-widget-content ui-helper-clearfix ui-corner-all" id="ui-datepicker-div"></div>

 

Since the div has borders so it looks like a bar.  Could anyone tell me how to get rid of it?

 

Thanks in advance!