// JavaScript Document

function textCounter(field, maxlimit) {
if (document.getElementById) {
  var aNumber = document.getElementById('myCounter');
} else if (document.all) {
  var aNumber = document.all['myCounter'];
}

if (field.value.length > maxlimit) // if too long...trim it!
field.value = field.value.substring(0, maxlimit);
// otherwise, update 'characters left' counter
else 
  aNumber.innerHTML= maxlimit - field.value.length;
}