Hehehe, I'm sure you know, good teachers make good students! :-)
Also, I don't try to remember all the codes. Instead, I've saved them in a piece of text file, from where I can copy-paste them into my blog. Of course, eventually I'm sure I'll remember them. The easiest ones like headings, centering, or bold I don't need to look up, still I have them saved just in case.
Oh nice! Thanks for this code to make the code invisible! Just what I needed for writing this post.
And as far as mistakes go, not all of them are real mistakes. For example, both centre and center are correct, the first one is British English spelling, the second one American English. You know, just like theatre or colour.