Wifi is ON. But browser does not work.

My wi-fi connection is on. It is the same one as my computer is using.
It is white.
But, my broswer seems to not be working. It says 'unable to connect to the Internet, please try again later. If the problem persists please contact your service provider'.
Everything seems to be working until yesterday night. Browser, Blackberry Messenger, Msn and Facebook does not work. It says there are some problems with my server. BUT! The weird thing is, my twitter seems to be working just fine. I've downloaded twitter for about two months, though.

Is there any way to fix this? Thanks in advance!