I'm using mPDF with PHPExcel. I'm trying to configure layout with CSS. I can't get anything to work.

```
// this has no effect
$pdf->SetDefaultBodyCSS('color', '#ff0000');

```

I also try to use external style sheet:

```
// in php
$stylesheet = file_get_contents('pdf_styles.css');
$pdf->WriteHTML($stylesheet,1);

// in pdf_styles.css
body {
    font-family: serif;
    font-size: 5pt;
    color: red;
}

```

Any help or hint would be highly appreciated!