if you neglected to save your css file in a .css format, then it may not work.

An extract from w3.org:

"The CSS Working Group is a team of W3C Member representatives and W3C Invited Experts who are responsible for maintaining the current CSS standards...."

When it comes to using CSS on the web it is the web page developer that decides whether to use CSS or not to. Unlike Javascript, CSS is not something an end user can choose to allow or not, unless they delete the CSS post-download so-to-speak using a browers plugin like Web Developer.

The styles css were not created by a specific person in general. They were created by a group call the World Wide Web Consortium.

DHTML is short for Dynamic HTML. It is a group of internet languages that work together. CSS is just one of those languages. You can write DHTML without CSS, but CSS is a part of the language that you can use It's pretty hard to use DHTML without it, but it is possible.