var cks = new Array();

function preload() {
  var ck_off = new Image;
  ck_off.src = "/images/check_on.gif";
}


function ck_toggle(num) {
  var im = document.getElementById('ck_' + num);

  if (cks[num] == 1) {

    cks[num] = 0;
    im.src = "/images/check_off.gif";

  } else {

    cks[num] = 1;
    im.src = "/images/check_on.gif";

  }

  location.href="cart_add.php?id=" + num + "&m=" + cks[num];
}