When working with elements having single class name I've noticed something weird.

Example.

<div id="head" class="head"></div>

$('#head').removeClass('head');

<div id="head" class=" "></div>

$('#head').addClass('head');

<div id="head" class=" head"></div>

So there's no way to compare element class name against some value let's say

if ($('#head').attr('class') == 'head') { ...

because the name of elemnt class is ' head' not 'head'

won't work for version 1.4.1 but it works OK for 1.3.2