Certain sites won't work for me for some reason..

[Syringer]

So there's 4 of us connected on a router, on the same internet connection, and for some reason the other 3 computers can always access certain websites whereas about 50% of the time I can't regardless of what browser I'm using.

Two of the sites that often go down for me are: shopzilla.com and salesforce.com

I can't for the life of me figure out why this could be, or what it could be caused by, or how I could go about solving it? Any ideas?

 

[Rebooted]

1. Try restarting the router. Unplug from power for 1 minute, re-plug.
2. Click on Start --> Run. Type in "CMD". Type in "ipconfig/flushdns".
3. Try the sites again.
4. If still not working, check the config on the router to see if there's a way you can clear up DNS cache.