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?