How do I go about creating a username checker like www.usernamecheck.com or www.namechk.com however, customize it for different sites. If you can help thank you.

i believe it has not much to do with javascript except it all those social networks/portals/whatever have an AJAX powered API/WebService. In that case you can use XmlHttp object for that.

IE doesn't support that, so you would also need the ActiveXObject But this is assuming you don't want to ignore any IE user on your site..

Cheers