yes,

I pinged www.bigapple.com. got

reply from 72.3.135.151:bytes=32 time=44ms ttl=50....

looks like the network works.

the thing is the explore says "cannot find the server"

the firefox says"unable to connect"

"if your computer or network is protected by a firewall or proxy, make sure that firefox is permitted to access the web". I don't know if proxy is the problem. I restarted router and PC, didn't work. thanks