add class to body on click.

header.php

				<span class="font-size" href="#">Font Size</span>
				<span class="black-white" href="#">Black and White</span	>

				<script src="<?php bloginfo('template_url'); ?>/library/js/libs/cooked.js"></script>
				<script>

					jQuery(document).ready(function($){
					    // Check (onLoad) if the cookie is there and set the class if it is
					    if ($.cookie('font-size') == "yes") {$("body").addClass("font-size");}
					    if ($.cookie('black-white') == "yes") { $("body").addClass("black-white");}
					    
					    // When the span is clicked
					    $(".font-size").click(function () {
					        // Check the current cookie value
					        // If the cookie is empty or set to no, then add font-size
					        if ($.cookie('font-size') == "undefined" || $.cookie('font-size') == "no") {
					            // Set cookie value to yes
					            $.cookie('font-size','yes', {expires: 7});
					            // Add the class to the body
					            $("body").addClass("font-size");
					        }
					        // If the cookie was already set to yes then remove it
					        else {
					            $.cookie('font-size','no',  {expires: 7});
					            $("body").removeClass("font-size");
					        }
					    }); 
					
					    // When the span is clicked
					    $(".black-white").click(function () {
					        // Check the current cookie value
					        // If the cookie is empty or set to no, then add black-white
					        if ($.cookie('black-white') == "undefined" || $.cookie('black-white') == "no") {
					            // Set cookie value to yes
					            $.cookie('black-white','yes', {expires: 7});
					            // Add the class to the body
					            $("body").addClass("black-white");
					        }
					        // If the cookie was already set to yes then remove it
					        else {
					            $.cookie('black-white','no',  {expires: 7});
					            $("body").removeClass("black-white");
					        }
					    }); 
					
					});