function maxLength(field,maxChars) { if(field.value.length >= maxChars) { try {event.returnValue=false;} catch (e) {} return false; } }  function maxLengthPaste(field,maxChars) { try {event.returnValue=false;} catch (e) {} if((field.value.length +  window.clipboardData.getData("Text").length) > maxChars) { return false; } try {event.returnValue=true;} catch (e) {} return true; }
//<textarea rows="5" cols="6" onKeyPress='return maxLength(this,"30");' onpaste='return maxLengthPaste(this,"30");'></textarea>