update reference to value of base line-height

docs/css.html

@@ -331,7 +331,7 @@ lead: "Fundamental HTML elements styled and enhanced with extensible classes."
 
     <!-- Body copy -->
     <h2 id="type-body-copy">Body copy</h2>
-    <p>Bootstrap's global default <code>font-size</code> is <strong>14px</strong>, with a <code>line-height</code> of <strong>20px</strong>. This is applied to the <code>&lt;body&gt;</code> and all paragraphs. In addition, <code>&lt;p&gt;</code> (paragraphs) receive a bottom margin of half their line-height (10px by default).</p>
+    <p>Bootstrap's global default <code>font-size</code> is <strong>14px</strong>, with a <code>line-height</code> of <strong>1.5</strong>. This is applied to the <code>&lt;body&gt;</code> and all paragraphs. In addition, <code>&lt;p&gt;</code> (paragraphs) receive a bottom margin of half their line-height (10px by default).</p>
     <div class="bs-example">
       <p>Nullam quis risus eget urna mollis ornare vel eu leo. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Nullam id dolor id nibh ultricies vehicula.</p>
       <p>Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec ullamcorper nulla non metus auctor fringilla. Duis mollis, est non commodo luctus, nisi erat porttitor ligula, eget lacinia odio sem nec elit. Donec ullamcorper nulla non metus auctor fringilla.</p>