If you have a problem opening some web pages these tips may help you. They are about to heal symptoms, not the cause. The cause is usually virus activity.

1. Open this branch of a registry: cmd-> regedit -> [HKey_Local_Machine\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\PersistentRoutes]
   It must be clean, except default entry.
2. Try this in Start/run: md /k notepad c:\WINDOWS\system32\drivers\etc\hosts
   It must be clean, except localhost entry.
3. Find faults in the pipeline: cmd /k tracert www.yourcite.com
   This tip doesn’t help to fix, but to diagnose.
4. Clear dns cache:
   cmd /k ipconfig /displaydns
   cmd /k ipconfig /flushdns
5. Install and run antivirus, for example, Kaspersky antivirus, trial version. http://www.kaspersky.ru/

References:

1. http://exler.livejournal.com/1385703.html
2. http://www.labnol.org/software/tutorials/computer-cannot-open-internet-websites/2116/