Spry

Specify a minimum and maximum number of characters

 To specify a minimum or maximum number of characters, add the minChars property or maxChars property (or both) and a value to the constructor, as follows:
<script type="text/javascript">
	var textareawidget1 = new Spry.Widget.ValidationTextarea("textareawidget1",{minChars:value, maxChars:value});
</script>