I have designed (with the help of the tutorial on this site) a script wich generates a cookie ($userid) through the loading of a gif-image (gif on homeserver.com, pages to trace on otherserver.com, homeserver.com, yetanotherserver.com, ...). Works fine and the cookie-value is readable by the script each time it loads. It is also readable by the domain on which the gif-script resides (homeserver.com)
Would it be possible to make the cookie-value public to the otherserver.com-domain too? In any way ?