Fender Stratocaster (with "Tremolo") bridges employ six screws at the front of the bridge plate to keep the bridge aligned properly and to fix the pivot point of the tremolo system.
Since the dawn of time, people have been taking out the four inside screws, leaving just the two outside screws to hold the bridge. These two screws are just barely tight.
This is because - with just two pivot points, the tremolo feels better, and the guitar stays in tune better. It has only been fairly recently that Fender has adopted the 2-point tremolo.
Decked versus Floating:
* Fender was famous for confusing Tremolo with Vibrato. Tremolo is a change in the amplitude of the guitar signal. Vibrato is a change in the pitch of the guitar signal.
The Fender guitar vibrato system was labeled "Tremolo".
The Fender amp tremolo system was labeled "Vibrato".
This drawing (not to scale) is a cross-section of a Fender Stratocaster - type tremolo system. In concert pitch, a set of 0.010 - 0.046 strings will generate 103.6 pounds of force. A "Floating" tremolo will have the rear of the bridge plate elevated 1/8" above the guitar body, In this way, the tremolo arm can be depressed, lowering the pitch of the strings, but it can also be lifted to raise the pitch of the strings. The force "x" on the tremolo springs (total) to exactly balance the force of the strings is 28.79 pounds.
It is generally accepted that a floating tremolo is difficult to tune and keep in tune. Tuning one string can throw the other strings out of tune, since the combined string tension changes. The advantage of a floating tremolo is that the tremolo arm can be both depressed and lifted, giving a wider pitch range vibrato effect.
It's personal preference, based on your playing style. Personally, I prefer a rock-solid blocked tremolo that doesn't move. I remove the tremolo arm and put it in the case. Tremolo is provided by the fingers.
A well known, large guitar store chain sets up all their guitars with floating tremolo. This can be frustrating for beginning guitar players because the guitar will go out of tune more often and can be more difficult to get back into tune. However, many experienced players rely on a floating tremolo to give them the full-range vibrato sounds that they are after - and it does sound nice.
This drawing (not to scale) is a cross-section of a Fender Stratocaster - type tremolo* system. In concert pitch, a set of 0.010 - 0.046 strings will generate 103.6 pounds of force. A "Decked" (or Blocked) tremolo will have the bridge plate flat against the guitar body, In this way, the tremolo arm can be depressed, lowering the pitch of the strings, but it cannot be lifted because the body prevents the bridge plate from moving n that direction. The force "x" on the tremolo springs (total) to exactly balance the force of the strings is 25.9 pounds. In order to prevent the tremolo from moving much at all, this force is usually increased by 10 pounds or more by tightening the tremolo claw screws. By adjusting the springs to about 26 pounds, the arm can be easily depressed for vibrato effect.
It is generally accepted that a decked tremolo will stay in tune better than a floating tremolo, and that string vibrations are more readily transmitted through contact with the guitar body.
With Carmen as the Demo Strat, here we see just two outside screws securing the bridge plate. Note that the 4 holes in the body do not exactly line up with the holes in the bridge plate.
Sometimes people with leave all 6 screws in, but back out the inner 4 .