The following is a CSS style example to create a box-shadow on three sides except for the top side.
HTML
<div id="shadowDiv">This is a three-sided shadow box.</div>
CSS
#shadowDiv { background-color: #ddd; margin: 0px auto; padding: 10px; width: 220px; box-shadow: 0px 8px 10px gray, -10px 8px 15px gray, 10px 8px 15px gray; }
Output
This is a three-sided shadow box.
To generate box shadow CSS code online, check this tool.