Most of the background style tags are pretty much self explanatory with a few exceptions.
When positioning a background item the horizontal position comes first followed by the vertical like this:
left is horizntal and top is vertical.
If more information is necessay they will be added with the next update.
Like I said before there are many way's to use css to enhance your web site design. Please use the resources and tools to help you achieve the site you desire. Also remember that css can make updating or changing your site much easier and quicker than standard html by using external sheets and only having to change one or two things instead of changing the same thing on all your pages. Especially if your site contains many pages.