Il faut utiliser l'attribut CSS2 overflow
<html><head><title>overflow</title>
</head><body >
<p style="width:70px; height:100px; overflow:auto; border:thin solid #804000">
bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla
</p>
</body></html>