http://cflove.org/2010/05/simple-jquery-textarea-maxlength-function.cfm
: <script type="text/javascript">
2: $( "document" ).ready( function ( ) { 3: $( 'textarea[maxlength]' ).live( 'keyup change' , function ( ) { 4: var str = $(this).val() 5: var mx = parseInt ( $(this ) .attr( 'maxlength' )) 6: if (str.length > mx) { 7: $(this).val( str.substr ( 0, mx ) ) 8: return false; 9: }})}) 10: </script>