My laptop misses keystrokes?

This is very common with laptops over time. You have some dirt building up under the keypad. Although you can take the keys off and thoroughly clean them, there is a much easier method. Use a can of air that you can get at best buy or any computer shop. Blow between the keys. It's best to put the computer at an angle so the dirt can actually come out from under the keys. I had the identical problem that you describe and with the canned air, I resolved it in about 30 seconds. Hope this helps!