function alertmsg() {
    alert("こんにちは");
}

function addidmsg(ev) {
    var kadai_element = document.getElementById("hello");
    if (kadai_element) {
	kadai_element.innerHTML += " こんにちは";
    }
}

function show(ev) {
  var element = (ev.target||ev.srcElement);
  element.style.backgroundColor = "white";
}

function addAll() {
  var i, item;
  var checks = document.getElementsByTagName("span");
  for (i=0; i<checks.length; i++) {
    item = checks[i];			
    if (item.getAttribute("class") == "check") {
      item.addEventListener("click", show, false);

    }
  }
}
window.onload = addAll;