function showAudio() {
	hide("video_content");
	hide("chat_content");
	show("audio_content");
	var button = getObj("button_audio");
	if (button) {
		addClass(button, "act");
	}
	button = getObj("button_video");
	if (button) {
		removeClass(button, "act");
	}
	button = getObj("button_chat");
	if (button) {
		removeClass(button, "act");
	}
}

function showVideo() {
	hide("audio_content");
	hide("chat_content");
	show("video_content");
	var button = getObj("button_video");
	if (button) {
		addClass(button, "act");
	}
	button = getObj("button_audio");
	if (button) {
		removeClass(button, "act");
	}
	button = getObj("button_chat");
	if (button) {
		removeClass(button, "act");
	}
}

function showChat() {
	hide("audio_content");
	hide("video_content");
	show("chat_content");
	var button = getObj("button_chat");
	if (button) {
		addClass(button, "act");
	}
	button = getObj("button_audio");
	if (button) {
		removeClass(button, "act");
	}
	button = getObj("button_video");
	if (button) {
		removeClass(button, "act");
	}
}