Quitar fecha de expiración a la cookie

[excitex]

Saludos,

Quisiera quitar la fecha de expiración a la cookie.

Os dejo el script por si alguien sabe como hacerlo.

<script LANGUAGE="JAVASCRIPT" TYPE="TEXT/JAVASCRIPT">

expireDate = new Date
expireDate.setMonth(expireDate.getMonth()+6)

cookieName = ""
if (document.cookie != "") {
cookieName = document.cookie.split("=")[1]
}

function setCookie() {
cookieName = "prueba"
document.cookie = "cookieName="+cookieName+";expires=" + expireDate.toGMTString()
}

// Delete the cookie
function deletecookie(){
if (document.cookie != "") {
thisCookie = document.cookie.split("; ")
expireDate = new Date
expireDate.setDate(expireDate.getDate()-1)
for (i=0; i<thisCookie.length; i++) {
cookieName = thisCookie[i].split("=")[1]
document.cookie = "cookieName="+cookieName + ";expires=" + expireDate.toGMTString()


}
}
}
// End hiding script -->
</script>

Gracias anticipadas