<form method="post">
    <input type="text" name="pseudo" id="pseudo" value="Pseudo" onclick="if(this.value='pseudo')this.value='';" onblur="if(this.value='')this.value='pseudo';" />
    <input type="password" name="mdp" id="mdp" value="password" onclick="if(this.value='password')this.value='';" onblur="if(this.value='')this.value='password';" />
    <input type="submit" name="connexion" value="Connexion" />
</form>