function nav_over(str) {
		elm_top = document.getElementById('nav_'+ str +'_top');
		elm_over = document.getElementById('nav_'+ str +'_over');
	if ( elm_over.className.indexOf('activ') < 0 ) {
		elm_top.className = elm_top.className.replace(/mc_b/g,'fc_b');
		elm_over.style.visibility = 'visible';
	}
}
function nav_out(str) {
		elm_top = document.getElementById('nav_'+ str +'_top');
		elm_over = document.getElementById('nav_'+ str +'_over');
	if ( elm_over.className.indexOf('activ') < 0 ) {
		elm_top.className = elm_top.className.replace(/fc_b/g,'mc_b');
		elm_over.style.visibility = 'hidden';
	}
}