I'd be very wary of following an online resource until you understand the background of strength training as you could do yourself a mischief if you blindly follow some exercises. They also tend to be rather poor as they assume you have s certain lever of knowledge when it comes to the subject. However, I can recommend
The Complete Book of Abs if you want to learn more about fitness. Yes, its a very cheesy American book but it also covers back exercises and general fitness as well as abs in a very clear, easy to follow way (with lots of pictures!
).