function doOnLoad() {

	// preload images
	preload('images/menu-home-over.png');
	preload('images/menu-about-over.png');
	preload('images/menu-properties-over.png');
	preload('images/menu-listproperty-over.png');
	preload('images/menu-contact-over.png');

}

// preloads an image
function preload(imgsrc) {
	var i = new Image();
	i.src = imgsrc;
}

function menu_over(that) {
	that.src = 'images/menu-' + that.name.substr(5) + '-over.png';
}
function menu_out(that) {
	that.src = 'images/menu-' + that.name.substr(5) + '.png';
}