hi,
Is your application using forms-based authentication? If that the case, you need to apply the <location> tag to the Web.config file to configure access to a specific file and folder. For instance,
<configuration>
...
<location path="yourCSSFolderPath">
<system.web>
<authorization>
<allow users="*"/>
</authorization>
</system.web>
</location>
</configuration>
Source:
http://support.microsoft.com/kb/316871[
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