Are you searching for a way to make text inside a container wrap to a new line and have the container expand downwards if needed?
Update
<div class="modal hide fade" id="modalRemoveReserve" style="display:none;">
<div class="modal-header">
<button class="close" data-dismiss="modal">×</button>
<h1>Test</h1>
<div style="border-bottom:1px solid #aaa;"></div>
<br />
<div id="reservesTextContainer">
Text here... lkjasflj fljas fsaj flsjfkd skl
</div>
</div>
<div class="modal-footer">
</div>
</div>
#reservesTextContainer {
width: 150px;
height: auto;
word-wrap: break-word;
border: 1px solid red;
}