Where do I find documentation/tutorial for the style sheets. 

Specifically, under the "stylesheet editor", there is this "/* text style for the selected tab */". 

What exactly is a "selected tab" mean?  (When I see the word "tab", I think of the "tab key" on my keyboard, but I have no clue what is a "selected tab" on a website is?.)

Thanks for your reply.  Okay, I then replace the word "tab" with "page"

/* text style for the unselected pages */   
/* hyperlink style for the unselected pages */

Yet I still don't understand.  What does "unselected pages" mean?  Does it mean pages that are not currently displayed by the browser?  If yes, then my question is why care what the text/hyperlink style is for pages that are not currently displayed by the browser.  If not, then what exactly is a "selected/unselected page"?

John, thanks for your reply.  My question is...

Why do I have to even care whether the page is active or not active?  I mean... for example, if I want the font size to be 13px for the pages, then I will set all the pages to have font size of 13px regardless of whether the page is active (current page that I am on) or non-active (the pages that I am not currently on).  

Why would there be a need to specifically set the font size (or anything else) of a page that is not active.  That doesn't make any sense to me.  I should not need to make any distinction between these 2 type of pages (active and non-active pages.) 

Can you or someone explain?  Thank you.