function lengthCountdown(field, maxlength)
{
 if (field.value.length == maxlength)
 {
  field.value = field.value.substring(0, maxlength);
  alert('Please keep your posting short!\n\nYou are limited to 600 characters (about 40 words).');
 }
 if (field.value.length > maxlength)
 {
  field.value = field.value.substring(0, maxlength);
  alert('You appeared to have attempted to paste in a large block of text.\n\nPlease start again and make a shorter posting.\n\nThe limit is 600 characters.');
  field.value = "";
 }
 else {
 eval('field.form.' + field.name+ 'Length.value = maxlength - field.value.length'); 
 document.getElementById('visibleCount').firstChild.nodeValue = maxlength - field.value.length;
 }
}