Cascading Style Sheets for web accessibility

Dear all,

I have found out that, some web sites which are designed in  Cascading Style 
Sheets (CSS)are accessible and easy to navigate.
Now, my questions are:
1. How much the CSS based sites are more accessible compare to the web sites 
designed in HTML?
2. Is the CSS recommendable to design  web site for accessibility? if yes 
how?
3. Is the Cascading Style Sheets would b easy to learn by blind person?
4. Where do I get material to know about CSS?

Thanks in advance.