Since HuSi is primarily a diary site, it is handy to be able to keep up with the diaries of users whose exploits you have decided to follow for one reason or another. Not everyone has the time to compulsively watch the diaries page all day, every day (though many try), so HuSi allows users to keep track of other users' diaries.
To watch a diary, simply go to a user's profile page and select "Watch <so-and-so's> diary". A link to this user's diary will appear on the right-hand side of your screen under the Watchlist category. If your Watchlist is not expanded by default, click on the Watchlist link, and links to all of the users you're watching, along with any stories you may be watching, will appear.
When one of the users on your watchlist posts a new diary entry, a link to that diary entry will appear under the user's name. The link will disappear when you click on it or when you click on the (clear) link next to that user's name. This keeps your watchlist from becoming unwieldy and annoying.
If you have a lot of people on your watch list, you can choose to hide the list of users who haven't posted a new diary. Just click the "Show only new entries" link.
To unsubscribe a user from your watch list you can either visit the users page, and click "Unwatch", or you can click the small "-" next to the users name on your watch list.