function change(tausch_bild_name,neues_bild_name, showreset, alt_txt)
{
window.document[tausch_bild_name].src = "Bilder/"+neues_bild_name+"";

window.document[tausch_bild_name].alt = ""+alt_txt+"";

if ( showreset ) {
  if (document.getElementById)
    document.getElementById("img_reset").style.visibility = "visible"; }
else {
  if (document.getElementById)
    document.getElementById("img_reset").style.visibility = "hidden"; }
}