Able to ping a website but its not opening in browser.
Possibilities : Deposition of browser cache, DNS cache, Cookies etc.
Shooting :
1. Try first by clearing the cache from the browser.
2. Try by clearing the DNS cache from the system.
c:\>ipconfig /flushdns
3. Enable /disable the internet connection.
4. Download winsockproxy software to fix this bug if happening regularly.