function update_chars_left() {
	var input = document.getElementById('new_slog_text');
	var output = document.getElementById('new_slog_chars_left');

	var chars_left = 250;
	var url_count = 0;
	var url_length = 0;
	var is_url = false;
	var chars_per_url = 14;

	for (var i = 0; i < input.value.length; i++) {
		if (is_url) {
			if (input.value.charAt(i) != ' ') {
				url_length++;
			}
			else {
				is_url = false;
			}
		}
		else {
			if ((input.value.substr(i, 7) == 'http://') || (input.value.substr(i, 4) == 'www.')) {
				is_url = true;
				url_count++;
				url_length++;
			}
		}
	}

	chars_left = chars_left - input.value.length + url_length - url_count * chars_per_url;
	output.innerHTML = 'noch ' + chars_left + ' Zeichen';

	if (chars_left <= 0) {
		output.style.fontWeight = 'bold';
	}
	else {
		output.style.fontWeight = 'normal';
	}
}