How is possible that the web site is down but the traceroute is ok?

What Is a Virtual-Host?

Some web-servers, like Apache, can be configured to use what's called virtual-hosting; essentially a local redirection service. In essence, it works like this: the web server(we're going to assume it's Apache2 in this case) will choose what documents to serve depending on what domain and/or IP address the request was from. For example: if you were to navigate to a website at example.com, the server may give you the web-files stored at /var/www/com.example, but if you navigate to another site at example-2.com it may serve you the files at /var/www/com.example-2. All that the server's doing here is changing what is called the document-root, which is essentially the directory of the domain "root" (ex. google.com = root dir., google.com/file/ = not root dir., but a folder stored in the root dir).

Why This Is Relevant

Now what this has to do with your situation: Your domain at http://xxx.bluehost.com may actually be pointing to the exact same server as someone elses website, but the server will respond differently because of your domain name; So when you perform a traceroute to that server it may still respond successfully, because Bluehost may have taken your website down only. And a fair warning: I've always suspected the hosts that offer a cheap web server plan will occasionally shut down the websites of their smaller clients to make room for their bigger clients (bandwidth, processing power, etc.). If you read your agreements and contracts, there's probably a clause that gives them the right to do this.

NOTE: Don't confuse a virtual-server - or virtual-computer - with a virtual-host. They are very different, although they have similar purposes. Also, my apologies if it sounds like I'm assuming you know nothing about web-hosting and what not, it's just easier to assume someone doesn't than to explain it later; and it gives information to people that may read this question later as well!

The website runs on a server process. When you shut down the server process, the server does not magically turn off. Also not when you misconfigure your firewall (and block port 80) neither does the server go off nor does the ICMP rule in the firewall get deleted.

Traceroute uses ICMP protocol to reach an address, and a HTTP server use HTTP protocol, different ports, and different approaches. I can reach an address via ICMP echo request but, if the port I'm trying to communicate is closed or freezed somehow, I'll get a timeout error. And if you're sure the server is up and the port is up (listening), is better to check the firewall rules then.