I use a different site, which will track/predict periods, ovulation and fertility days (with cute little bunnies)

www.mymonthlycycles.com

You can even set it to send you an email to remind you your period is due, so you remember to put an extra pad/tampon in. I put in my info/symptoms each month, and now I know when the period is due (you can predict a few months ahead), when I ovulate, and if/when I need it, I will know when my fertile days are. This is a good place to start, and I've heard a lot of good things about the book mentioned above.