Don't qualify IDs, don't use multiple elements w/ same ID, and more!

Level 21: 

Change first instance of #fancy plate to be a bento box.  Why? 

1) We shouldn't encourage devs to have multiple elements with same ID in dom. 

2) This now visually demonstrates how the counting works
    board: "(1)(2)[x](3){4}(5)"
instead of
    board:"(1)(2)[3](4){5}(6)"

This nuance is lost when the third element is another fancybox, since the counting remains the same. 


Level 3:

Add in some text explaining that ul#long is redundant, and that you can just use #long.  Qualifying ids less performant, and shouldn't be encouraged 

Level 10:

Add in a short warning about using the * selector.  Since CSS is read right-to-left, this ends up querying all elements in the DOM, and can be detrimental to page speed.  A short warning about this was merited. 


I'm not sure if Level 3 and Level 10 changes are what you wanted the focus of CSS Diner to be.  There's a lot of quirks/quick tips that *could* be provided in this format, but it was kept relatively clean and devoid of commentary.