It is probably because the tank, as you describe it, is new and so it is just beginning to cycle. Cloudy water is normal during this time; that is called a "bacteria bloom" and would be the development of the beneficial bacteria that will help your fish feel more comfortable in the tank. It will clear up once your tank has finished cycling, so don't worry.
Here's some more information about the cycling process:
http://www.firsttankguide.net/cycle.php
http://www.algone.com/cycle.php
Also, from my own personal experience I found that while my tank is cycling, if I disturb the gravel in any way (i.e. while siphoning it) the water becomes cloudy, since I have also disturbed the bloom of the beneficial bacteria. It all settles down back at the bottom in a few hours, though.
By the way, what kind of fish do you have? Your tank might be overcrowded since a 10 gallon is quite small. That's another story, however.