The other day, my CD player would spit out any burned CD I put into it and say E20 on the display. I tried putting an actual CD in it, and that worked fine. Then I tried the burned CDs once more and it was fine again. What was up with my CD player?

Usually, the E20 message means that the lense needs cleaning. CD-Rs tend to be a little more difficult to read, so that would be why it'* happening with your burned discs.

On my Aurora with the Regular Ac-delco CD player, E20 meant clean lens or lens malfuntion. For me, Mine died, that when I bought my first Alpine. Ahhh memories, look what the E20 code turned me into.