How to show a gloabl message on a user profile page (in back end)?

add this code to your function.php

<?php
function showMessage($message, $errormsg = false)
{
    if ($errormsg) {
        echo '<div id="message" class="error">';
    }
    else {
        echo '<div id="message" class="updated fade">';
    }
    echo "<p><strong>$message</strong></p></div>";
} 

function showAdminMessages()
{
    showMessage("This is my message.", true);
}
add_action('admin_notices', 'showAdminMessages');
?>