Having done the St John's ambulance CPR and First Aid course, I'd say no. Sorry, but you can't learn how to correctly tie a tourniquet or perform CPR by pictures or video. Now, it is better than nothing but I'd say take an afternoon and take the real life course. It will be well worth it.
I took it via work and funny enough, the next week I saw someone get hit by a car and jumped right in. A very short time later a doctor arrived, asked me what happened and what I was doing and he said "great job". I wasn't able to work on the guy's head so he went to work there, I just stabilized his shattered leg and hip......
I concur with tboy on this one. If you find any online first aid training, it won't be worth anything. Go with a course offered by the Canadian Red Cross or by St.John Ambulance.
