function change_main_bkg(type) {
	var file = "";
			
	switch (type) {
		case "sale":
			file = "url('img/main-sale-bkg.png')";
			break;
		case "food":
			file = "url('img/main-food-bkg.png')";
			break;
		case "safe":
			file = "url('img/main-safe-bkg.png')";
			break;
	}
		
	document.getElementById('main').style.backgroundImage = file;
}

function show_submenu (menu_id) {
	document.getElementById(menu_id).style.display = 'block';
}

function hide_submenu (menu_id) {
	document.getElementById(menu_id).style.display = 'none';
}

function show_div(div, form) {
	document.getElementById(div).style.display = "block";
	
	var x = screen.availWidth/2 - 400;
	document.getElementById(form).style.left = x + "px";
}