You have some invalid HTML which is the probable cause of the problem: the
</head> tag needs to be placed after the </style> tag.
Note that you should really be adding a doctype to your page, for two reasons: the first is that having a doctype will allow you to validate your page and spot coding errors such as the above more easily. The second is that, for anything more than very basic CSS, the presence of a full doctype ensure the browser will follow the standards closely when parsing the page, making the behavior of the CSS much more consistent cross-browser.
The best doctype for you is probably this one:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">