Event.observe( window, 'load', function ( ) {
  $$( '#MainNavigation li a' ).each( function ( e ) {
    if ( !e.up( 'li' ).hasClassName( 'active' ) ) {
      $( e ).observe( 'mouseover', function ( ev ) {
        var img = Event.element( ev );
        img.writeAttribute( 'src', '/images/' + img.id + '_over.gif' );
      } );
      $( e ).observe( 'mouseout', function ( ev ) {
        var img = Event.element( ev );
        img.writeAttribute( 'src', '/images/' + img.id + '.gif' );
      } );
    }
  } );

  $$( '#LandingPageNavigation li a' ).each( function ( e ) {
    if ( !e.up( 'li' ).hasClassName( 'active' ) ) {
      $( e ).observe( 'mouseover', function ( ev ) {
        var img = Event.element( ev );
        img.writeAttribute( 'src', '../images/' + img.id + '_over.gif' );
      } );
      $( e ).observe( 'mouseout', function ( ev ) {
        var img = Event.element( ev );
        img.writeAttribute( 'src', '../images/' + img.id + '.gif' );
      } );
    }
  } );
} );