Setting cookies with javascript?

how do i set a cookie with javascript?

this is what i have:

var cookie_date = new Date ( );
document.cookie = "clickcookie=clicked; expires=" + cookie_date.toGMTString();

Code (markup):

this doesnt seem to work. what am i doing wrong? i want to set a cookie called "clickcookie"...and i want it to expire in 30 days

 

How do you know it's not working? Keep in mind that you can't see the cookie on the same page load.