function enviarForm()
{
    $('form_contacto').request(
    {
        onSuccess: function(t)
        {
            var dialog = new Element('div');
            dialog.insert(new Element('img', {src: 'img/contacto_ok.jpg'}));
            var overlay = new DialogOverlay(dialog);
            overlay.show();
        }
    });

}

function DialogOverlay(content, container) {
 
	// Manage arguments and assign defaults,
	if (typeof container == 'undefined' ) container = document.body;
	if (null == (this.container = $(container))) throw("container is not valid");
 
	// Assign instance variables
	this.content = content;
	this.overlay = new Element('div', { 'class': 'overlay' }).hide();
	this.dialog = new Element('div', { 'class': 'dialog' }).hide();
 
	// Hide the overlay when clicked. Ignore clicks on the dialog.
	Event.observe(this.overlay, 'click', this.hide.bindAsEventListener(this));
	Event.observe(this.dialog, 'click',  this.hide.bindAsEventListener(this));
 
	// Insert the elements into the DOM
	this.dialog.insert(this.content);
	this.container.insert(this.overlay);
	this.container.insert(this.dialog);
 
	// Content may have been hidden if it is embedded in the page
	content.show();
	this.dialog.hide();
}
 
DialogOverlay.prototype.show = function() {
	new Effect.Appear(this.overlay, { duration: 0.5,  to: 0.8 });
	this.dialog.show();
	return this;
};
DialogOverlay.prototype.hide = function(event) {
	this.dialog.hide();
	this.overlay.hide();
	return this;
};