CSS word long within the div

[provaands]

Defects of the code below:
with Mozilla, Netscape, the word hellooo..... exit outside from the div;
with IE 5,5, 6 the word hellooo.... increase the width of the div, even
if i have fixed to 100px the width;

Question:
can I make so that word hellooooo..... remains all within to the div?
I do not want to use overflow in order to see the text with the sliding bar,
but it must to increase the height of the div, so the div can to contain
all the word hellooo.....
on more rows;
I have tried to put heigth=auto but it does not change null;

<div style='width:200px;background:green;'>

<div style='width:100px; background:#99CCFF;'>

hellooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
</div>

<div style='width:100px; background:silver;'>
by by
</div>
</div>

thank you