Need help with typing errors

Hello,
Okay so I have a inspiron 1420. Works good but having typing problems on my laptop. When I am
typing on Notepad or this message for example my keyboard is working totally fine. Yet when I go onto my gmail account and type and email my keyboard skips letters, the space button wont work the first time i hit it, and the backspace does not work. So when i type my message is missing letters and I have to click things many times before it ever appears on my screen. This also happens when I am on facebook. But anywhere on my computer or sites like this it works beautifully. Whats the problem and how can i fix this