First you need webspace that supports php (
)
Then you need to learn some basic PHP coding (
Here and
Here)
Then you need to make a .htaccess 404 page that points 404's to blah.php (
.htaccess 404)
Then make blah.php so that it takes $_SERVER['REQUEST_URI'], sticks it onto
http://www7.hattrick.org, and loads it with php function fread() (function search
Here)
If you need to forward and bounce back HTTP headers like cookies, POST, etc, use CURL (function search curl, again,
Here)