This is usually caused by your site referencing an external resource such as an audio file, a video file, or CSS. This explains why some of your sites which do not encounter this error load successfully but without CSS. Try putting an "In-line" CSS on your page and it shows perfectly.
This is due to the fact that your website or application hosted in IIS is not allowed to "Read" an external resource.
To fix this, you would have to go to your IIS Manager. To run IIS Manager, click Start on your taskbar, then run "inetmgr".
More information on running IIS Manager here
Then expand the
Go to "Home Directory" or "Directory"(In Win98) Tab and enable or check "Read" checkbox. And you're done!
