function isNumber(field)
{
	var re = /^[-]?\d*[\.\,]?\d*$/;
	if (!re.test(field.value))
	{
		alert('Der må kun stå tal i feltet');
		field.value = field.value.match(/^[-]?\d*[\.\,]?\d*/)[0];
	}
}

function delayed_log_off(url, seconds)
{
	var command = "location.href = '" + url + "'";
	setTimeout(command, seconds * 1000);
}