Apply "float: left" to the .thumbnail rule. This will force each of the divs over to the left edge of the containing box or until it hits the edge of another div. A width is also required when floating an element - unless it is an image.
CSS CODE
.thumbnail
{
float: left;
width: 60px;
}
HTML CODE
<div class="thumbnail">
<img src="images/image.gif" alt="" width="60" height="60"><br>
Caption
</div>
<div class="thumbnail">
<img src="images/image.gif" alt="" width="60" height="60"><br>
Caption
</div>
<div class="thumbnail">
<img src="images/image.gif" alt="" width="60" height="60"><br>
Caption
</div>
<div class="thumbnail">
<img src="images/image.gif" alt="" width="60" height="60"><br>
Caption
</div>
<div class="thumbnail">
<img src="images/image.gif" alt="" width="60" height="60"><br>
Caption
</div>
<div class="thumbnail">
<img src="images/image.gif" alt="" width="60" height="60"><br>
Caption
</div>