Server not found or not responding

Hello,



I have windows 7 i had my laptop for about a year now (Dell Inspiron 15R) i am connected to the internet because there is a home CPU in my living room, my brother also has laptop and uses the same connection, sometimes i cant open my browser. It says "server not found or not responding" something like that. It stays like that for a couple of mins to HOURS AND HOURS. It happens like every day. I use safari by the way. But my brother has NEVER had that happened to him. He uses Mozilla Firefox He's never even had internet problems, my laptop is newer than his and everything, what could be the problem ? Also , we are like 6 feet away from each other in the same room, using the same connection. Please and thank you !