ti posto tutta la pagina così faccio prima:
codice:
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1"> 
        <title>Titolo</title>
        <link rel="stylesheet" href="jquery.mobile-1.0.css" />
        <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
        <script type="text/javascript" src="jquery.mobile-1.0.min.js"></script>
        <style type="text/css">
            .pdv_h4, .pdv_p {
                font-size: 10px;
            }

            .pdv_h4 {
                color: #f445a5;
            }
        </style>
    </head>
    <body>
        <div data-role="page" class="type-interior" data-theme="a">
            <div data-role="content">
                <div data-role="fieldcontain">
                    <h4 class="pdv_h4">TESTO</h4>
                    <p class="pdv_p">
                        Testo - Testo

                    </p>
                </div>
            </div>
        </div>
    </body>
</html>
qualsiasi font-size metto dentro al cellulare rimane sempre uguale.
nel pc invece cambia.