I stumbled across this issue multiple times during my life of web developer (which begun about 10 years ago), it appeared every now and then to complicate things when I was in the middle of a heavy debugging sessions and doing frequent changes to my pages; I was expecting some kind of results but despite the fact that the code was looking good, there were no signs of those changes. Sometimes even adding a new UI element like a button or an image or changing the color of a header had no effect...

Having a look at the page source within IE demonstrated the browser was somehow right not showing the new image or color because it was not there in the code... where was that source coming from?

Well, if it does not come from the web server, then it's loaded from the IE local cache... so let's go to Internet Options > General > Delete > Temporary Internet Files, give it another try and guess what? This time it works...! So, not sure why, but for some reason IE was not refreshing its case and was using an outdated version of my pages. Then after a while I forgot about problem.