$(document).ready(function() {

  $('a.menuitem').click(function() {

      var arr = 0;

      var link = $( this ), url = link.attr( href );

      var newDiv = $( document.createElement( 'div' ) )

      $( #content_pane ).append( newDiv );

      newDiv.load( url );

      return false;

  });

});

As you can see I am creating a div and adding some content to it, how would I give each div that is created a unique id, something like section1, section2, section3, etc?