Why do some of the keys on my keyboard not work?

One of the problems may be that there is debris under the key which is preventing it from being able to be pushed down. Try to tip you computer upside down and shake the debris out. If this does not solve the problem, then you can try to use compressed air to blow the debris out. Finally, if you can still not get the key to type, you may want to consider removing the keyboard in order to clean out the debris blocking the key. Try checking out the Device Troubleshooting page for more additional help: Dell Inspiron M5110 Troubleshooting