function clearAndSetField(field){
	if(!field.isSet) {
		field.isSet = true;
		field.value = '';
		field.style.color = '#000';
	}
}
function replaceMessage(field, message){
	if(field.value == ''){
		field.style.color = '#999';
		field.value = message;
		field.isSet = false;
	}
}