When using CSS, you can link the stylesheet to your HTML using the 'link' tag (pure HTML) or you can use the @import directive.
Which of these 2 is the best, one might think? Well, the answer can be determined by the browsers you are targetting with your site. The @import is currently understood by every modern browser, however, if your visitors (or at least some...) are still using Netscape Navigator 4, you are better of using @import.

Why is that? Well, NN4 does a terrible job rendering CSS, even up to a point where it makes CSS enabled webpages unreadable. However, it doesn't understand the @import directive and thus ignores CSS. This way, you can make this 'error' an advantage: it will render your page, though it will not look good, it will at least be readable!