I always tell my kids that the most important thing to know is how to find answers to the stuff you don’t know. I would add that it is also helpful to know where to find references to the things you know, but don’t need to memorize.
Here are some of my handy references:
For how to make a horizontal list (I can never keep this nugget in my brain)
http://css.maxdesign.com.au/listamatic/horizontal01.htm
For color help:
http://colorschemedesigner.com/
For MySQL help when moving a site to a new domain/server:
http://www.mydigitallife.info/how-to-move-wordpress-blog-to-new-domain-or-location/