@import url(css/layout.css);

<!-- The @import Hack. Early browsers are notorious for malfunctioning when presented with CSS rules they can't handle. The import hack allows you to hide entire stylesheets from version 4 and older browsers by linking them with a method they don't understand: the @import rule. The @import rule links to an external stylesheet from within a stylesheet (external or in a STYLE element), however, early browsers do not understand the syntax and simply ignore the statement (and the stylesheet it references). All CSS1 browsers will load abasic.css and acss.css, however, only modern browsers will understand the @import rule and also load nav.css and layout.css. Since nav.css and layout.css are linked after abasic.css, their rules will override those in abasic.css more easily.
-->