function mainmenu(){
$(" #jNav ul ").css({display: "none"}); // Opera Fix
$(" #jNav li").hover(function(){
		$(this).find('ul:first').css({visibility: "visible",display: "none"}).show(400);
		},function(){
		$(this).find('ul:first').css({visibility: "hidden"});
		});
};

 $(document).ready(function(){      
    mainmenu();

    var randomNumber = Math.floor(Math.random()*4) + 1;  
    var background = '/images/home_background_' + randomNumber + '.jpg';
    $("body").css("background-image", "url(" + background + ")");

});