connected through wifi but unable to browse and use installed apps

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http://androidforums.com – Hi guys please help me, I can connect with wifi, but Im unable to browse using any browser and so as my installed apps like facebook, google playstore,Ym etc. Whenever i try to browse an error appeared that i must check my wifi network settings. when I try to use my facebook apps it says "connection lost". Wifi signal is great though.. :c My OS is android gingerbread. Thanks in advance! (General)