my browser can’t find some server

About for 2 months, i can’t access some sites (getting message “can’t establish a connection to the server at” OR “can’t find server at”)like bleach-network.com and animetake.com on my laptop from GoogleChrome, Firefox, safari even IE. I don’t know why because previously it was just fine. Then i tried using Opera, it loads fine only when i turn on opera turbo. But if i turn off Opera Turbo, i can’t access the site and get message “Couldn’t locate remote server”. Why can this be happen? Does that means their server are down? Tried to unplug all the network connection for 15 seconds & turn off source power but still the same.