function radioSelected(radio) {
	for (var i = 0; i < radio.length; i++) {
		if (radio[i].checked)
			return radio[i].value;
	}
	return '';
}

function validatePetition(form) {
	var errorText = '';
	var errorField = null;
	
	if (form['First'].value == '') {
		errorText += '\t- enter your first name\n';
		if (errorField == null) errorField = form['First'];
	}
	if (form['Family'].value == '') {
		errorText += '\t- enter your family name\n';
		if (errorField == null) errorField = form['Family'];
	}
	
	var affil = radioSelected(form['Affiliation']);
	if ('' == affil) {
		errorText += '\t- indicate your affiliation\n';
		if (errorField == null) errorField = form['Affiliation'];
	}		
	if (('Faculty' == affil) && (form['Department'].value == '')) {
		errorText += '\t- please indicate your U of C department\n';
		if (errorField == null) errorField = form['Department'];
	}
	
	if (errorField != null) {
		alert('Please address the following errors:\n' + errorText);
		if (errorField.focus) errorField.focus();
		if (errorField.select) errorField.select();
		return false;
	}
	
	return true;
}