function setMaxLength() {
        var x = document.getElementsByTagName('textarea');
        var counter = document.createElement('div');
        counter.className = 'counter';
        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>/'+x[i].getAttribute('maxlength');
                        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 = this.value.length;
        
}
this.relatedElement.firstChild.nodeValue = currentLength;
        // not innerHTML
}