Found this one Apple forum, might want to give it a try.
Jul 12, 2012 1:23 PM (in response to EkanaKoka)
I may have the solution, at least its been working for me. If you go into settings and choose Network and then tap the blue arrow on the right of the wifi network you usually use you'll come to settings for the network. Someone told me that the intermittent not finding the web page and then later finding it sounded like a DNS resolution problem. He told me to change the DNS setting. I suggest you first write down the number in the DNS slot, generally a sequence of numbers separated by periods/full stops. Delete that number. Then enter this number... 208.67.222.222
This number is for the OpenDNS which is an organisation which supplies free DNS services (you do a web search for opendns and read about it at for example wikipedia). For some reason our ISP's DNS servers are having trouble resolving certain DNS addresses (eg,
www.bbc.co.uk) for a certain period of time. OpenDNS is probably a more robust service than your ISP's DNS servers. It's working for me, no hangs all day. If you want you can always re-enter the DNS number which you wrote down earlier and you haven't lost anything. Works for me.