how to set rotation of camera?

ok im trying to make a camera move but i dont want to use the first person controller prefab for it. the problem is that every time i move the camera up and sideways at the same time it anglesall wired like tilting your head. i figured the easiest way to fix this would be to set the cameras rotation on the x axis to 0 every frame. how do i do that without affecting the y or z?