I've sent in many bug reports about this in many exercises. I'll copy and paste my last one to sum this up.
"Step 8 says to "Visit http://localhost:8000/messages in the browser. Click on New Message to add a message of your own." This is not possible. In the browser interface on the right, you can click the back arrow. This only retrieves the last typed URL. You can click the refresh arrow. This appears to do absolutely nothing. There's the URL bar in which you can type URLs. Hitting enter does nothing and acts as if you clicked the green "Run" button at the bottom-center of the screen. There's an enlarge button. This enlarges the blank, empty browser to become fullscreen.
So tell me. How am I supposed to visit http://localhost:8000/messages in the browser?"
Here's a picture of how this appears on my end: http://i.imgur.com/VJhtOrG.png
Another frustrating problem is repeatedly seeing "look at the diagram on the right" and only seeing a huge, blank, white space like the one in the picture above. How many pages worth of information have I missed out on just because the interface is glitched? I may never know.
Yet another frustrating problem is how weird it feels to perform 8 steps in a row, either writing or copying and pasting over 1 full page of code, and not knowing how huge chunks of it work because none of it is being explained. Some 15 or so new concepts are all being introduced simultaneously in the same exercise and interacting with each other in various ways, and there's no explanation on how they function. As such, I'm obviously not learning anything; I'm just copying and pasting what I'm being told to copy and paste. I wonder if those invisible diagrams would have explained any of these things... What a depressing feeling this is.
These problems exist for me across multiple browsers, including chrome and firefox.