var buttonImage = null;

function f_mouseOverButton(element) {
    var src = "";
    var dir = "";
    var file = "";
    var ext = "";

    buttonImage = new Array();
    
    src = element.src;

    dir = src.substring(0, src.lastIndexOf("/") + 1);
    file = src.substring(dir.length, src.lastIndexOf("."));
    ext = src.substring(src.lastIndexOf("."));

    buttonImage["src"] = src;
    buttonImage["file"] = file;
    
    src = dir + file + "_a" + ext;
    
    element.src = src;
}

function f_onMouseOutButton(element) {
    var src = "";
    var file = "";

    if (buttonImage != null) {
        src = element.src;
        file = src.substring(src.lastIndexOf("/") + 1, src.lastIndexOf("."));
    
        if (file == (buttonImage["file"] + "_a")) {
            element.src = buttonImage["src"];
        }
    
        buttonImage != null;
    }
}