Despite the fact it didn't help, just a short explanation:
1. Shift-Reload (should) tell the browser not to use the cache.
2. No. Because there might be an In-Memory cache too. But I see: You're using IE!? I have no experience with that. Sorry.
3. Exactly. This is to verify you receive the correct CSS.
4. If this happens when you open the pasted code, then nothing can be wrong - to my understanding - with your code. It must be a caching problem because the only difference is the source where you get your page from.
Try to sniff on the traffic that's going on between your server and your browser and see what they are "talking" about.
But at least try to access your Server from another computer that never visited those URLs...