Hi and Welcome.
What phone are you using ?
What website are you trying to access.
Also ensure your handset firmware is up to date.
Try using a different browser on your phone.
I use both safari and google chrome.
1st check your Apn settings which are dependant on wether your on contract or PAYG.
Turn your phone off and remove the battery if possibe then turn back on.
Remove your sim and give it a wipe down.
If your on PAYG ensure you have data left in your tariff.
Check you have some form of internet symbol in your status bar which if ok should be the 3g logo or an alternative to indicate edge or gprs coverage.
Check the mast status where you reside by using this link:
http://status.o2.co.uk/
Contact 02 Customer Services from your mobile by ringing ;
Contract Customer : 202.
PAYG Customer : 4445.
To ensure your account is ok.
