"Normally, the browser returns cookies only to the same hostname that sent them. You can use setDomain method to instruct the browser to return them to other hosts within the same domain. To prevent servers from setting cookies that apply to hosts outside their domain, the specified domain must meet the following two requirements: It must start with a dot (e.g., .prenhall.com); it must contain two dots for noncountry domains like .com, .edu, and .gov; and it must contain three dots for country domains like .co.uk and .edu.es."