if (document.images) {

    training_by_date_up       = new Image();
    training_by_date_up.src   = "images/training_date.jpg" ;
    training_by_date_down     = new Image() ;
    training_by_date_down.src = "images/training_by_date_rollover.jpg" ;

    training_by_topic_up       = new Image();
    training_by_topic_up.src   = "images/training_topic.jpg" ;
    training_by_topic_down     = new Image() ;
    training_by_topic_down.src = "images/training_by_topic_rollover.jpg" ;
    
    signup_up       = new Image();
    signup_up.src   = "images/signup.jpg" ;
    signup_down     = new Image() ;
    signup_down.src = "images/signup_rollover.jpg" ;
}
function buttondown( buttonname )
{
    if (document.images) {
      document[ buttonname ].src = eval( buttonname + "_down.src" );
    }
}
function buttonup ( buttonname )
{
    if (document.images) {
      document[ buttonname ].src = eval( buttonname + "_up.src" );
    }
}