Actually a subject. More specifically: there is a website, you need to write a script on it that will enter user-defined text in a textarea on another website. For example livejournal.
If only the browser will track. Through php and js hardly get.
If the second site is not yours, then nothing. For this only browser plugin
Look where the action forms are on the site where the field is located, and create your own form with the same address, and if there are no referral checks, etc., and this is hardly possible in the livejournal, then send the text straight there :)
Yes, and you can fake a referral.