404 entries in log files

[eluser]dimethroxy[/eluser]
I have a problem with CI error logging. CI is adding 404 errors for page that are perfectly valid.

Here is my yesterday log:

Code:

...
ERROR - 2010-01-12 21:54:55 --> 404 Page Not Found --> styles
ERROR - 2010-01-12 21:55:11 --> 404 Page Not Found --> styles
ERROR - 2010-01-12 21:55:25 --> 404 Page Not Found --> styles
ERROR - 2010-01-12 21:55:29 --> 404 Page Not Found --> styles
ERROR - 2010-01-12 21:55:31 --> 404 Page Not Found --> styles
ERROR - 2010-01-12 21:55:41 --> 404 Page Not Found --> styles
ERROR - 2010-01-12 21:56:17 --> 404 Page Not Found --> styles
ERROR - 2010-01-12 21:56:21 --> 404 Page Not Found --> styles
ERROR - 2010-01-12 21:56:35 --> 404 Page Not Found --> styles
ERROR - 2010-01-12 21:57:11 --> 404 Page Not Found --> styles
...

Almost every page result in a 404 entrie in the log file, even if they are valid and does not output 404 in the web browser!

Got any idea?

Thanks.