On www.tongguitar.co.kr you can see in the Net tab in Firebug (Firefox):
GET www.tongguitar.co.kr, Status: Aborted
GET www.tongguitar.co.kr, Status: Aborted
[...]
GET www.tongguitar.co.kr, Status: Aborted
GET www.tongguitar.co.kr, Status: 200 OK
It does not happen always, but only sometimes and I don't know why. I use PHP and MySQL and Apache. Is it a server-side problem, a DNS problem? Is there an error in the PHP source code?
Sometimes this will happen if you have simple things like CSS rollovers (your roll over an image, the request is sent, but you move one before the response is returned) or if your page's JavaScripting requests a resource but doesn't wait for a response to return. Often, the latter is related to a JS analytics call. It's also been known to happen when you hit to "Stop" button.
Either way, it's not an error. It's just part of how the browser uses HTTP.