Usage: improved preamble

Author: carlosame

usage.html

@@ -31,9 +31,14 @@
 <div id="presentacion_top" class="textheader"><span>Usage</span></div>
 <div class="cos">
 <h1>CSS4J User Guide</h1>
-<p>This project is an implementation of W3C's <a href="https://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/" target="_blank">CSS Object Model API</a>
-in the Java&trade; language, and also adds CSS support to the <a href="https://dom4j.github.io/" target="_blank">DOM4J</a> package. It
-targets several different use cases, with functionalities from style sheet error detection to style computation.</p>
+<p>This project implements, in the Java&trade; language, APIs that are partly based on W3C's <a
+href="https://www.w3.org/TR/cssom-1/" target="_blank">CSS Object Model</a> and WHATWG/W3C's <a
+href="https://dom.spec.whatwg.org/" target="_blank">DOM</a> APIs. (Initially, the project
+implemented the <a href="https://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/"
+target="_blank">DOM Level 2 Style API</a>.)</p>
+<p>It targets several different use cases, with functionalities ranging from style sheet error
+detection to style computation. A specialized module also adds CSS support to the <a
+href="https://dom4j.github.io/" target="_blank">DOM4J</a> package.</p>
 <p>Java 8 and later versions are supported (the library is fully modular).</p>
 <div class="tema" id="overview">
 <h2>Overview</h2>