[jQuery] .length value different in IE vs FF

[Bob O]

I have a pretty simple character counter to count the number of
character typed by a user..

    broadcastSubmit = $('#broadcastSubmitButton');
    broadCastMessageDiv = $('#broadcastMessage');
    availableChars = 140;
    charCount = $('.char_count');
    boilerPlateKeyword = $('#boiler_plate_keyword');
    boilerPlateKeyword.text(keyword.toUpperCase());

    broadCastMessageDiv.bind('keyup', function() {
      broadCastDiv = $(this).val();
      previewContentWindowTextLength = broadCastDiv.length;
      boilerPlateText = $('#boiler_plate').val();
      boilerPlateTextLength = boilerPlateText.length;
      charCount.text(availableChars - (boilerPlateTextLength +
previewContentWindowTextLength) - 0);
    });

This basically has a div with some preset text. (reply stop keyword to
cancel.)
and then a textarea that a user types an SMS message into. it combines
the user input with the preset text and subtracts it from the total
character limit (140)

my problem is IE is correct in the count, but FF and Safari are equal,
but wrong. they are showing more characters than there should be.

e.g.  after typing in a message IE might be 28 available chars and
Safari and FF would be 20

Why would those browsers add more to the count? any ideas.