When compression is enabled on a server running Internet Information Services (IIS), and an HTTP request is served from the IIS compression directory, a 0-byte file may be returned instead of the expected file.
Note You may only see these symptoms if HTTP Static Compression is enabled.
Antivirus software running on the IIS server is scanning the IIS compression directory.
Exclude the IIS compression directory from the antivirus software's scan list. The steps to do this may vary based on the antivirus software you are using. Microsoft recommends that you contact the manufacturer of the antivirus software for information about how to exclude directories from scanning.
The default compression directory in IIS 6.0 is %systemroot%\IIS Temporary Compressed Files. This directory may have been changed to another location. In IIS 7.0 or a later version for IIS 7.0, the default location of the compressed file cache is %SystemDrive%\inetpub\temp\IIS Temporary Compressed Files.
To verify the compression directory:
Click Start, point to Programs, point to Administrative Tools, and then click Internet Information Services (IIS) Manager.
In IIS Manager, right-click the Web Sites folder, and then click Properties.
Click the Service tab.
Under HTTP Compression, make sure that Compress static files is selected, and then locate the path to the temporary directory.