Rename the file to index.html.
A Web host typically has a list of default file names that it will serve if a site is requested by the domain name alone. The name index.html is very common, as are index.htm, default.html, and default.html. When a server gets a request for just a domain, it will go down the list of default names and return the first one it finds. If you don't have your main (home) page named with one of the default names, the server can't find it and so returns an error.
If someone requests something like www.mydomain.com/health.html, then the server would return that file. But health.html is not a standard default file, so someone requesting simply www.mydomain.com wouldn't get the file you intend.
There's a related question here: http://forums.adobe.com/thread/906880?tstart=0