websites don't open on a specific wifi connection (probably DNS issue)
Some users have reported similar problems with 10.10.2

Looking true you attempts, I would suggest following additional steps.

Reset WiFi settings:

Turn Off Wi-Fi from the Wireless menu item

From the OS X Finder, hit Command+Shift+G and Copy/Paste the following path:

/Library/Preferences/SystemConfiguration/


Select following files: 

com.apple.airport.preferences.plist

 com.apple.network.identification.plist

com.apple.wifi.message-tracer.plist 

NetworkInterfaces.plist 

preferences.plist

and move them to Desktop (do not delete for now). This forces OS X to recreate all network configuration files. 

Restart WiFi and check.

Solution 2:

If your Ping works (your WiFi connection is fine), then check and modify your DNS server (responsible to connect you to the right website). I would add Google DNS in system preferences- Network -Advanced -DNS and it is the 8.8.8.8