function DropDown() {
	if (document.getElementById('drop_down_menu').style.display == 'block') {
		document.getElementById('drop_down_menu').style.display='none'; 
		document.getElementById('MenuBar').style.backgroundImage ='url(images/MenuBar/MainBtnOff.jpg)';
		return true;
	} else  {
		document.getElementById('drop_down_menu').style.display='block'; 
		document.getElementById('MenuBar').style.backgroundImage ='url(images/MenuBar/MainBtnOn.jpg)';
		return true;
	}
	return false;
}