function createXMLHttpRequest( ) {
	try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) {}
	try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) {}
	try { return new XMLHttpRequest( ); } catch(e) {}
	// alert("XMLHttpRequest not supported");
	return null;
}

form_comprar = {
	 iniciar: function() {
		aComprar = $('#a_comprar');
		divForm = $('#div_form_comprar');
		divForm.style.display = 'none';
		aComprar.href = 'javascript:form_comprar.activar()';
	}
	,activar: function() {
		divForm = $('#div_form_comprar');
		divForm.style.display = 'block';
		form = $('#form_comprar');
		//form.action = "javascript:form_comprar.proc";
	}
}