It hurts readability when you put bright colored font over a white background. I checked the codecademy courses on my phone and it also has this very ugly combination of colors as well. I’m 100% sure it didn’t look like this before, it had bright text over a black background.
What browser are you using? Have you tried emptying the browser cache and/or disabling any extensions? Is your browser up-to-date? Have you changed any settings recently? Have you tried switching browsers?
There is a recent report by another student of a similar issue: Django help please