Landing page throws 404 error but inside pages works

When I type the URL as www.example.com, it throws the following error message.

404 - File or directory not found. The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable.

but when I type the URL as www.example.com/index.cfm, it works. When I open the URL www.example.com from the server, it throws different error message.

HTTP Error 404.17 - Not Found The requested content appears to be script and will not be served by the static file handler.

The DefaultDocument in IIS is already set to index.cfm. Please advise what can be the problem and how can I solve this issue.