function changeSection(key) {

	var sections = jQuery('.section');
	
	for (var i = 0; i < sections.length; i ++) {
	
		sections[i].setAttribute("class", "section");

		sections[i].setAttribute("className", "section");
	
	}
	sections[(key-1)].setAttribute("class", "section activa");

	sections[(key-1)].setAttribute("className", "section activa");
	
	var links = jQuery('.link');
	
	for (var i = 0; i < links.length; i ++) {
	
		links[i].setAttribute("class", "link");

		links[i].setAttribute("className", "link");
	
	}
	links[(key-1)].setAttribute("class", "link activa");

	links[(key-1)].setAttribute("className", "link activa");
	
}