Use input type `password` for the password field in the CSS documentation.

css.html

@@ -1169,7 +1169,7 @@ For example, <code>&lt;section&gt;</code> should be wrapped as inline.
         <label for="exampleInputEmail">Email address</label>
         <input type="text" id="exampleInputEmail" placeholder="Enter email">
         <label for="exampleInputPassword">Password</label>
-        <input type="text" id="exampleInputPassword" placeholder="Password">
+        <input type="password" id="exampleInputPassword" placeholder="Password">
         <label for="exampleInputFile">File input</label>
         <input type="file" id="exampleInputFile">
         <p class="help-block">Example block-level help text here.</p>