I am answering this question in response to your other question via a comment on one of my answers. I begin by saying that landing proceedures vary highly among different aircraft due to size, weight, speed, elevation, and landing gear configuration. Some planes such as taildraggers have to be landed with a slightly different pitch angle than others. Touching the nose wheel down is the real issue, you risk rupturing a tire or in the case of single engine aircraft, damage to the prop. Now to the other question, "Why do aircraft such as the 747 land with the nose up and undercarriage visible?" This answer is slightly more complex. During descent from cruising altitude, a variety of things are taking place. Power may be adjusted, (could be reduced to glide down) flaps and slats may be extended at various levels to put drag on the plane.(which then would require some power increase for control) The descent rate and airspeed are carefully monitored during this stage, certain minimums must be met to avoid a stall, but at the same time, a max airspeed for the plane and flight level cannot be exceeded. With all this in mind, during final for runway, the nose is pitched up because at such low altitudes and airspeeds, pitch is used to control the descent rate, avoid stalls, and keep the airspeed within the correct margin. When the nose of the plane rises (pitch up) the descent rate drops, allowing the plane to touch down as gentle as possible. Once the rear landing gear is on the ground, airspeed must be further reduced, descent rate halted, speed brakes deployed, and lift must be completely lost. To put it as simple as possible, it is possible for an aircraft to be still flying with all of the wheels on the ground. Nose up pitch avoids descending into the ground too hard, since the plane is still flying. Once the wheels contact, lift has to be killed and the nose eased down. If this is not clearly understandable or anyone has further questions, please post them as a comment here and I will revise or add new answers as needed.

ha... ive landed some hundred thousand times... either as pilot. copilot or passenger... and i can assure you ive seen it all. and yes...its not only possible but probable that youve done it too as a passenger... i can tell you with 99% acccuracy if a pilot is an air force navy or civilian by the way they hit the "dirt". navy pilots are taught to "stick it" on carriers and put everything on the deck at the same time.including my stomach. ive landed as a passenger to thousands of former seadogs landings and when you hit hard , its usually an ex navy pirate,... doing the job. as a former airline exec, weve spent millions repairing or replacing parts on landing gears, rammed home by the nations "best". ha.