Can someone tell me why this is not working? I already used CSS validator and HTML validator and both passed 

header.xhtml

```
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html
        PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
    <title>Header</title>
    <link rel="stylesheet" type="text/css" href="header.css"/>
</head>
<body>
    <div>
        <a id="logo" href="index.php"><img src="includes/images/crown-automotive.jpeg" alt="Crown Cars World"></img></a>

        <div id="ownerLogin">
            <a href="ownerPage.php">owner login</a>
        </div>
    </div>
</body>
</html>

```

header.css

```
#logo
{
    display: none;
}

```