If this happens, you might want to adjust your saddle fore/aft. If your center of gravity is not balanced, you will not accelerate as efficiently as you could. Your front wheel shouldn't be lifting off, but your weight shouldn't be leaning on your hands either.
You want to adjust the saddle position so that you can comfortably change your posture so that you can optimally move your center of gravity for each situation- from seated to sprinting or climbing.
Here's a link to give you an idea:
http://www.sheldonbrown.com/kops.html