function try_button_off() {
    document.try_button.src = "/main/images/try_button_off.png";
}
function try_button_on() {
    document.try_button.src = "/main/images/try_button_on.png";
}
function buy_button_off() {
    document.buy_button.src = "/main/images/buy_button_off.png";
}
function buy_button_on() {
    document.buy_button.src = "/main/images/buy_button_on.png";
}
function download_button_off() {
    document.download_button.src = "/main/images/download_button_off.png";
}
function download_button_on() {
    document.download_button.src = "/main/images/download_button_on.png";
}