Many of you experience this frustrating problem, when you have Full Wi-Fi Signal but nothing would boot up in Internet Browser or Play Store or Facebook etc... all you gonna get is Connection Error
Thats due to your I9100 being unable to get IP Address from router.
What requires to do, is manually assign IP Address to your Galaxy S2,
that is simple can be done with third party app from Google Store, such as WiFi Manager by Kostya Vasilyev.
Once you've obtained the app, run it and find your Wireless Network that you would like to connect
Enter you password first.
Then Tick box with "Show Advanced Settings"
two new option will drop out
The one you need is "Assign IP Address" tick that box
Here is screen shot of my setting which are pretty standard for most users out there with home routers, however i would like you to check setting and local ip address on you Router, Lapton or other wireless device first.
One thing i should mention that "Address" Line is IP address that you going to assign to your Galaxy Phone must not be take by other wireless device.