How do I add custom CSS to individual pages?
Well the absolute simplest way is to look at the body class using firebug or developer tools with chrome.

You will see something like this:

&lt;body class="html not-front logged-in no-sidebars page-node page-node- page-node-19 node-type-log-node admin-menu"&gt;


Which as you can see even has the node id for the page. Then its just a simple case of using

.page-node-19 {
background: #000000;
}


Or whatever!

And, if you want to get super in detail with adding stuff to certain pages, themes, regions, dependencies on which users etc etc then look into the context module and all its related modules.