i was wondering if it's possible to use a high voltage ceramic capacitor for a 5V ldo, I also will use a 0.33uF 250V ceramic capacitor for the input. thaanks
You most certainly can. A ceramic capacitor will actually give you the pretty close to the advertised capacitance if you only apply a small percentage of its rated voltage.
A ceramic capacitor's effective capacitance degrades with voltage so if you were to apply 275V to your .1uF capacitor, you would unlikely get much more than .05uF of actual capacitance. In your case you will get very close to .1uF. However, your design will be very non-optimal as the size of the capacitor is probably enormous and you'd be better off getting a smaller one.
It will work.
But that is a lot of derating!
It is actually a good idea to use components rating higher than what they are exposed to, it will stress them less, and they will last longer. Now, 2 or 3 times is more usual (e.g. a cap rated 16V on a 5V line is plenty) ... a factor of 50+ might be a little overkill ;)