function setMaxLength() {
	var x = document.getElementsByTagName('textarea');
	var counter = document.createElement('div');
	counter.className = 'Contador';
	for (var i=0;i<x.length;i++) {
		if (x[i].getAttribute('maxlength')) {
			var counterClone = counter.cloneNode(true);
			counterClone.relatedElement = x[i];
			counterClone.innerHTML = '(<span>0</span> caracteres restantes)';
			x[i].parentNode.insertBefore(counterClone, x[i].nextSibling);
			x[i].relatedElement = counterClone.getElementsByTagName('span')[0];
			
			x[i].onkeyup = x[i].onchange = checkMaxLength;
			x[i].onkeyup();
		}
	}
}

function checkMaxLength() {
	var maxLength = this.getAttribute('maxlength');
	var currentLength = this.value.length;
	if (currentLength > maxLength) {
		this.value = this.value.substring(0, maxLength);
		currentLength = maxLength;
		alert('O texto ultrapassou o limite de 255 caracteres.');
	}
	this.relatedElement.firstChild.nodeValue = maxLength - currentLength;
	// not innerHTML
}