Drupal catches all URL requests!

Edited to add: The following is only relevant if you have Drupal installed directly in your web root and not in a directory. If Drupal is in a directory, it is just not possible to affect another parallel directory. If they are parallel directories, Drupal has nothing to do with it and you just need an .htaccess file in /ifm containing a DirectoryIndex index.php line.

If Drupal is directly installed in your web root, the following applies.

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Check the .htaccess file which is in your public_html. If Drupal itself works, then the DirectoryIndex line is OK and the culprit is probably that last block of lines:

# Rewrite current-style URLs of the form 'index.php?q=x'.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?q=$1 [L,QSA]

Do you have these lines? The two RewriteCond lines tell Drupal not to interfere if it is a real file or a real directory. There is a caveat though. If it is a real directory but does not contain an index file as specified in the DirecoryIndex line, then this directive is ignored and Drupal does interfere.

You can make it bulletproof by disabling those two lines with a # and putting this in their place:

RewriteCond %{REQUEST_FILENAME} !-U

This should work, except if there is some other modification in your public_html/.htaccess file.