We get tons of support requests from people that have little to no experience with html and other codes used in the templates.
http://www.w3schools.com/ is a great resource for learning how to code.
I suggest you look at the following pages before you get into editing the templates:
HTML
XHTML
Javascript
DHTML
CSS
Edit by Staff: Some of the above links are no longer valid as of March 28, 2014 therefor we recommend you view W3S's sitemap -
http://www.w3schools.com/sitemap/default.asp in order to see what tutorials are available

.