Here's a screenshot of some selects and the CSS that runs them. These are just basic selects, with no extra divs or other tricks. The CSS shown is the whole lot. There's nothing else used.
/* Inputs, etc. */
input, textarea, button, select {
font: 100%/150% "Segoe UI", "Helvetica Neue", "Liberation Sans", "Nimbus Sans L", Arial, sans-serif;
color: #444;
}
And:
#userarea select {
margin: 0 2px 0 0;
padding: 0;
width: 8em;
}
#background_select>select {
margin-top: 4px;
}