You mean your porn bookmarks? Why not just drag and drop the url/bookmarks to a folder on your drive, and then RAR/ZIP it with a password? Or even better, drag and drop your bookmarks to a RAR file, and store it on an SD card hidden in a CD case or something. --- Oh sh!t, I've said too much haven't I....
I know it's old, but I had to search everywhere to find a specific easy to use answer to accomplish this task. It is quite simple. You can use the firefox Link Password add-on. It will even randomize those bookmark names that you are trying to password protect. Works like a charm.