function aktivni() {
	var soud_jinde = document.getElementsByName('fir_soud')[0].selectedIndex == 7;
	var soud = document.getElementsByName('fir_soud')[0].selectedIndex != 7;
	var silver = 'silver';
	
	document.getElementsByName('fir_zivnost')[0].disabled = soud;
	if (soud) document.formreg.fir_zivnost.value = "";
	document.getElementsByName('fir_zivnost')[0].style.backgroundColor = soud_jinde ? '' : silver;
}