As long as it doesn't get past 100C you should be fine with. The GPU is used for hardware accelerated video playback which explains why your card goes to 46C, a perfectly safe temperature.
I see a best answer here/\(that one). With web browsers being hardware accelerated as well as online videos being hardware accelerated, even surfing the net puts a bit of load on your video card(and takes some load of the cpu).
Yes, it is a GPU utility, not a mixed drink.
Some refer to Furmark as a "power virus". It simulates gpu usage(and power consumption) even the hardest to play games can not match, but it will not hurt your card(the card has been built with that in mind).