window.onload = function() {
        if(document.getElementsByTagName) {
          var inputs = document.getElementsByTagName('input');
          for(var i in inputs) {
            var input = inputs[i];
            if(input.type == 'password') {
              toggle_control = document.createElement('label');
              toggle_control.innerHTML = "<br /><input type=\"checkbox\" "+
                                         "onclick=\"toggle_password('"+
                                         input.id+"',this.checked)\" />"+
                                         " パスワードを隠さず表示";
              input.parentNode.insertBefore(toggle_control, input.nextSibling);
            }
          }
        }
      }
    
      function toggle_password(element_id, show_text) {
        if(document.getElementById) {
          var password_input = document.getElementById(element_id);
          var new_input      = document.createElement('input');
          with(new_input) {
            id        = password_input.id;
            name      = password_input.name;
            value     = password_input.value;
            size      = password_input.size;
            className = password_input.className;
            type      = show_text ? 'text' : 'password';
          }
          password_input.parentNode.replaceChild(new_input,password_input);
        }
      }