function swapDisplay () {
    if (!document.getElementById("extBlock")) return;
    var bool = (document.getElementById ("extBlock").style.display != "none");
    document.getElementById ("extBlock").style.display = bool ? "none" : "block";
    changeImage ("extButton", "/common/images/button_" + (bool ? "plus" : "minus") + "_02.gif");
    deleteRestoreImage ("extButton");
    document.getElementById ("extButton").alt = document.getElementById ("extButton").title = bool ? "全部見る" : "閉じる";
}
addWindowListener ("load", swapDisplay);