I am having problem while loading the CSS file through App_Themes folder but with ASP.NET authentication doesn’t work. The solutions are two. First it’s insert in web.config this tag:

<configuration> <location path="App_Themes/YourThemeFolder"> <system.web> <authorization> <allow users="*"/> </authorization> </system.web> </location> </configuration>

The second solution (that it’s always working) is changing tag page on web.config.

<pages styleSheetTheme="YourThemeName"> </pages>