how to add css and js in magento

first put your css and js in your project and and path is:-
skin\frontend\default\default  in css folder paste your css and make js folder this path and paste your js

and after call in head.phtml

 open this path  app\design\frontend\base\default\template\page\html\head.phtml
 and and of the page in  head.phtml

css link:-
<link href="<?php echo $this->getSkinUrl('css')?>/yourcssname.css" type="text/css" rel="stylesheet" />
js link:-
<script src="<?php echo $this->getSkinUrl("js")?>/yourjsname.js" type="text/javascript"></script>