Doujinshi is amateur manga publications, featuring either a cast of original characters and plot or characters from another manga or an anime (a 'fan manga').
Before that, i'd like to say sorry. Your lost gallery collections (fav, bookmark) cannot be recover anymore, the 2 disks that we had on the server got suddenly crushed and now it's unreadable. :(
As you noticed Loli, Oppai, Toddler, Shouta, Straight Shota tags are gone. Actually, they are not totally gone. I have disabled them for the meantime and only registered users with at least 2 weeks...