Force Ajax.gif Requests to Correct Location - A common one is requests for a file called ajax-loader.gif, probably evil scanning looking for poorly made ajax applications in which to exploit. Make sure that file really does exist and force all requests for it to that real location.
# REDIRECT AJAX-LOADER <ifmodule mod_rewrite.c> RewriteCond %{REQUEST_URI} !^/images/ajax\-loader\.gif [NC] RewriteCond %{REQUEST_URI} ajax\-loader\.gif [NC] RewriteRule (.*) [R=301,L] </ifmodule>