if (document.images)
{
  preload_image_object = new Image();
  // set image url
  image_url = new Array();
  image_url[0] = "_images/1-overview.gif";
  image_url[1] = "_images/1-overview_over.gif";
  image_url[2] = "_images/2-seminar.gif";
  image_url[3] = "_images/2-seminar_over.gif";
  image_url[4] = "_images/3-speaking.gif";
  image_url[5] = "_images/3-speaking_over.gif";
  image_url[6] = "_images/4-dates.gif";
  image_url[7] = "_images/4-dates_over.gif";
  image_url[8] = "_images/5-who.gif";
  image_url[9] = "_images/5-who_over.gif";
  image_url[10] = "_images/6-contact.gif";
  image_url[11] = "_images/6-contact_over.gif";
  image_url[12] = "_images/7-registration.gif";
  image_url[13] = "_images/7-registration_over.gif";
  image_url[14] = "_images/8-sponsors.gif";
  image_url[15] = "_images/8-sponsors_over.gif";

  var i = 0;
    for(i=0; i<=3; i++) 
      preload_image_object.src = image_url[i];
}


if (document.images) {
    overviewup       = new Image();
    overviewup.src   = "_images/1-overview.gif" ;
    overviewdown     = new Image() ;
    overviewdown.src = "_images/1-overview_over.gif" ;
    seminarup       = new Image();
    seminarup.src   = "_images/2-seminar.gif" ;
    seminardown     = new Image() ;
    seminardown.src = "_images/2-seminar_over.gif" ;
    speakingup       = new Image();
    speakingup.src   = "_images/3-speaking.gif" ;
    speakingdown     = new Image() ;
    speakingdown.src = "_images/3-speaking_over.gif" ;
    datesup       = new Image();
    datesup.src   = "_images/4-dates.gif" ;
    datesdown     = new Image() ;
    datesdown.src = "_images/4-dates_over.gif" ;
    whoup       = new Image();
    whoup.src   = "_images/5-who.gif" ;
    whodown     = new Image() ;
    whodown.src = "_images/5-who_over.gif" ;
    contactup       = new Image();
    contactup.src   = "_images/6-contact.gif" ;
    contactdown     = new Image() ;
    contactdown.src = "_images/6-contact_over.gif" ;
    registerup       = new Image();
    registerup.src   = "_images/7-registration.gif" ;
    registerdown     = new Image() ;
    registerdown.src = "_images/7-registration_over.gif" ;
    sponsorup       = new Image();
    sponsorup.src   = "_images/8-sponsors.gif" ;
    sponsordown     = new Image() ;
    sponsordown.src = "_images/8-sponsors_over.gif" ;
}
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" );
    }
}