finding information about an IP address on the web

Today i need to find information about an ip address, i got from internet. This thing can also happen when you get any spam or something from an ip and you need information about that ip. ARIN WHOIS Database Search helped me to get more information about ip. following is the URL of it:
http://ws.arin.net/whois/

For example if you want to know whom 216.239.51.99 ip belongs, you can type this ip in left text box on the site and on clicking submit query button you will have complete information.

HTML/JavaScript: Dynamically populating combobox/select options

I got a problem that how to dynamically populate values in html combo box using javascript. Or rather say, how to dynamically add options in select element of html.
here is our html code:

<select id="id_s">
 <option value="a">first</option>
 <option value="b">second</option>
</select>

Now suppose i want to add one option ‘third’, here is the code for it:

var combo = document.getElementById('id_s');
combo.options[2] = new Option ("third", "c");

Courtesy : This forum.