This will add a simple widget which displays just a small message.
add_action('wp_dashboard_setup', 'register_my_dashboard_widgets');
function register_my_dashboard_widgets() {
wp_add_dashboard_widget('myInfo_widget', 'Important Information', 'display_infoWidget');
}
function display_infoWidget() {
echo '<p>At the first of february this site gets a new design.
Therefore is wont be available this day. To see the current progress you can visit
<a href="http://www.justanexample.com" >this site</a></p>';
}