land1_on = new Image ( );
land2_on = new Image ( );


land1_off = new Image ( );
land2_off = new Image ( );

land1_on.src = "images/landing-button-on_10.jpg";
land2_on.src = "images/landing-button-on_12.jpg";
land1_off.src = "images/landing-button-off_10.jpg";
land2_off.src = "images/landing-button-off_12.jpg";

function button_on ( imgId )
{
  if ( document.images )
  {
    butOn = eval ( imgId + "_on.src" );
    document.getElementById(imgId).src = butOn;
  }
}

function button_off ( imgId )
{
  if ( document.images )
  {
    butOff = eval ( imgId + "_off.src" );
    document.getElementById(imgId).src = butOff;
  }
}