boton_preus_on_cat      = new Image();
boton_preus_on_cat.src  = "/sanmartin/images/btpreuscat.jpg";
boton_preus_off_cat     = new Image();
boton_preus_off_cat.src = "/sanmartin/images/btpreuscat2.jpg";

boton_preus_on_esp      = new Image();
boton_preus_on_esp.src  = "/sanmartin/images/btpreusesp.jpg";
boton_preus_off_esp     = new Image();
boton_preus_off_esp.src = "/sanmartin/images/btpreusesp2.jpg";

boton_preus_on_uk      = new Image();
boton_preus_on_uk.src  = "/sanmartin/images/btpreusuk.jpg";
boton_preus_off_uk     = new Image();
boton_preus_off_uk.src = "/sanmartin/images/btpreusuk2.jpg";

function rolloverPreusCat(img){
  img.src = boton_preus_off_cat.src;
}
function rolloutPreusCat(img){
  img.src = boton_preus_on_cat.src;
}

function rolloverPreusEsp(img){
  img.src = boton_preus_off_esp.src;
}
function rolloutPreusEsp(img){
  img.src = boton_preus_on_esp.src;
}

function rolloverPreusUk(img){
  img.src = boton_preus_off_uk.src;
}
function rolloutPreusUk(img){
  img.src = boton_preus_on_uk.src;
}