Internet Connection

My MacBook Pro is having problems to connect to internet using wi-Fi!! The Wi-Fi is indicating that it is connected in my laptop, but it has no access to internet. I checked with other two laptops (PC type) and they connected without a problem!! What could be the problem with my MacBook Pro?? Does the speed of the ISP has something to do with it??

I will appreciate your possible answer to this problem!!!

Thanks, asfinol