function IngrandimentoFoto(url, w, h) {
	window.open(url,'ingrandimento_foto','left=100,top=100,width='+w+',height='+h+',resizable=yes');
}

function IngrandimentoFotoHD(url, w, h) {
	window.open(url,'ingrandimento_fotohd','left=100,top=100,width='+w+',height='+h+',resizable=yes');
}

function IngrandimentoPubblicazione(url, w, h) {
	window.open(url,'ingrandimento_pubblicazione','left=100,top=100,width='+w+',height='+h+',resizable=yes');
}

function IngrandimentoServizioHD(url, w, h) {
	window.open(url,'ingrandimento_serviziohd','left=100,top=100,width='+w+',height='+h+',resizable=yes');
}

(function($) {
  var cache = [];
  $.preLoadImages = function() {
    var args_len = arguments.length;
    for (var i = args_len; i--;) {
      var cacheImage = document.createElement('img');
      cacheImage.src = arguments[i];
      cache.push(cacheImage);
    }
  }
})(jQuery);

jQuery.preLoadImages("img/sfondo1.jpg", "img/sfondo2.jpg", "img/sfondo3.jpg");

jQuery(document).ready(function() {
	var images = ["img/sfondo1.jpg", "img/sfondo2.jpg", "img/sfondo3.jpg"];
	var imageidx = Math.floor(Math.random()*3);
	jQuery('#header').css('backgroundImage','url(' + images[imageidx] +')'); 
});