This should help you:
Create a network codex

@deepikakumari, yes it works with WordPress 3.3.1

There is no need to complicate things when you have something instant for your solution, this is not worthy. If you use custom solution and there is problem then you will chasing your tail trying to fix it alone but using plugins you can ask in forum support and they will provide better plugin release. Use multi-site plugin instead of custom solution, here is the link: WordPress › Enable Multi-Site « WordPress Plugins