Cookies ???

I've been reading the threads under SETCOOKIE (from php.net) -- some people are saying that setcookie doesn't seem to work for all browsers all of the time. Then some others go into how it seems to actually be the TIME format (unix time vs. GMT time) -- Should I just stick to the HEADER version instead of setcookie? Also -- I'm not completely clear on how cookies work in the first place... Q1: When I set a cookie, is that cookie automatically called from *each* page on my website? Or, do I need to add the HEADER to each page where I want to call the cookie? Q2: The 'Cookie Path' -- is this the PATH on my websever -- someone please explain what this is exactly, and how it works. Q3: The scenario I would like to use cookies in is to have users automatically be logged in when they come to my home page... so I will need to store the Username and Password in the cookie... should I store these in an Array, or can I create multiple cookies -- in other words, a cookie can only store one value, correct? So, I can use Serialize / Unserialize to store Array information in my cookies? Thanks. Jason