Best flea prevention treatment that I can buy online?

[imalostcause]

I have 2 cats and 1 dog. The cats do go outside, although not much at this time of year. I've been buying Frontline, but read somewhere that it doesn't work as well as it used to, so wondered what is the best I can buy online?

I've used Advantage this year. It seemed to work well when we discovered a flea infestation.
Link, but shop around for best prices

Thanks

You'd need a prescription from the vet to buy online but I prefer Advocate to Advantage as it covers most types of worms as well.

Frontline's a bit crap, the fleas have become immune.

If you want to buy online, without a prescription, I'd recommend Advantage.