Bad news: You can’t!
Good news: We can work around it, assuming that you are:

1. a web developer trying to test your website in its eventual domain name
2. able to ping the IP address, but the browser unable to resolve the host name

The trick is we modify the Http Header’s Host value, then browse the IP address directly.

In Google Chrome, we can do this by using this plugin: ModHeader

Here’s how it looks like:

This way you can have many entries, and activate only one that you need. Don’t forget to deactivate all entries once you finished testing. If not, your browser won’t work.

If you’re using Firefox, you can use this extension: Modify Headers. This plugin offers more functionalities such as Start/Stop the Headers modification, enabling/disabling individual Header entries, etc.

If you’re using Opera, Safari or Internet Explorer, you might want to use Fiddler. It’s all-in-on suite to debug http traffic, which I personally found it an overkill since what we want is just to modify the Http Headers 🙂 Too bad I’m still unable to find plugin/addons similar to what Chrome and Firefox has. Let me know if you find one.