iphone.mydomain.com doesn´t have anything

hi i would like to know why when I acces to my domain iphone.mydomain.com i get a index.php. I mean a page in blank

i've configured everything according whit the video tutorial. I made it step by step and nothing happens

please help me

I'm using joomla 1.5 and I bought a CPAnel hosting

I don't know what to do and I don't want to change my server files

excuse my english BTW
it's not my native language