Can't set style of header row

galcott

I'm just starting with DataTables and created a test page using demo_table.css for styling. I would like to set the font weight and background color of the header row but it never changes. This is the section of the css that should apply but the font is not bold and the background is white. What am I doing wrong?

table.display thead th {
padding: 3px 18px 3px 10px;
border-bottom: 1px solid black;
font-weight: bold;
cursor: pointer;
background-color: #CC66FF;
}