I am developing a web-based database that needs to be opened through firefox web browser(because of some css3 elements). I want the page to open automatically in full screen mod
You will want to look at Fullscreen APIs of the browser. If you accept a small request/info to the user in the application it can be done quite easily. You just can't force the user into Fullscreen mode against his will. This is good (for security reasons).
http://hacks.mozilla.org/2012/01/using-the-fullscreen-api-in-web-browsers/