I think you are safe and those are coyote (maybe dog) tracks. The most telling item is the claw marks which as discussed on this website are usually not seen 'cause cats usually walk with them retracted.
http://www.bear-tracker.com/caninevsfeline.html
Here is some info on coyote tracks.
http://library.thinkquest.org/05aug/00260/.../pawprints.html
I am far from an expert on this sort of thing, it just we have both in our area and I always check out the tracks when they get too close to the house.
My uphill neighbor saw a cougar walking down the middle of road at 9 AM a couple years ago. The downhill neighbor watched one walk along the wall of his garage last year. His neighbor came home one night and the dogs and horses were going nuts so they called the police, everyone looked around and saw nothing until they looked on top of the horse trailer and saw a cougar looking down at them. The folks across the street fom them were watching the deer at a salt lick in their front yard a few years ago while drinking wine on the patio and a cougar came out from their left and chased away the deer, less than 30 feet away.
I found fresh tracks in the snow a few times and although I am not sure what it was, it was spooky when they disappeared behind a garden shed and didn't come out again.
The cougars here have never hurt anyone, neither have the coyotes; but any outside pet is assumed to be temporary. If the ground predators don't get them, the hawks, eagles or owls do. Our frineds with little dogs have lost one and the other hone has claw marks on their back where a big bird tried to get 'em. They watched as a Golden Eagle or Red Tail Hawk swooped down and took up one of their dogs a few months ago.
We keep track of the kids when they are outside and feel they are safe, it's not like we put a T-bone around their neck. I prefer the big cats over the gang members in the city any day, the cats are at least predictable. The coyotes here are well feed on rodents and cats so they are no threat to humans.
What is really spooky is when a mountain lion fights with a pack of coyotes; probably over a deer carcass or such. The cougar wail sounds like a woman screaming and the coyote howls are always un-nerving; I think it is part of our nature to fear that sound.
Anyhow, that's my critter rant for the day.