Here's the CSS (its actually a PHP file):

-- cut --
<?php
if (preg_match("/MSIE/", $_SERVER['HTTP_USER_AGENT']))
{
    $browser = "IE";
}
elseif (preg_match("/Firefox/", $_SERVER['HTTP_USER_AGENT']))
{
    $browser = "Firefox";
}
else
{
    $browser = "Other";
} ?>

body {
    margin: 2em;
}

pre, div, form {
    margin: 0;
}

/* tab menu unordered list */
ul#tabMenu {
    margin: 0 0.1em 0 0.1em;
    padding: 0.2em 0.5em 0.2em 0.5em;
    font: bold 14px Arial;
    border-bottom: 1px solid #aaa;
    list-style-type: none;
}

/* all tabs */
ul#tabMenu li {
    display: inline;
}

/* active tab */
ul#tabMenu li.active {
    color: black;
    background-color: #f7f7f7;
    margin: 0 0.3em 0 0.1em; /* ie only */
    margin: 0 <?php echo (($browser == "IE") ? "0.3em" : "0.1em"); ?> 0 0;
    border: 1px solid #aaa;
    border-bottom: 1px solid #f7f7f7;
<?php
    if ($browser == "Firefox") { ?>
    -moz-border-radius-topleft: 5px;
    -moz-border-radius-topright: 5px;
<?php
    } ?>
}

/* non-active tab */
ul#tabMenu li a, ul#tabMenu li a:visited {
    color: #aaa;
    background-color: #f7f7f7;
    margin: 0 0.1em 0 0.1em;
    padding: 0.2em 0.5em 0.2em 0.5em;
    text-decoration: none;
    border: 1px solid #aaa;
<?php
    if ($browser == "Firefox") { ?>
    -moz-border-radius-topleft: 5px;
    -moz-border-radius-topright: 5px;
<?php
    } ?>
}

/* hovered-over tab */
ul#tabMenu li a:hover {
    color: #f7f7f7;
    background-color: #ccc;
    text-decoration: none;
}

/* this makes the hovered-over tab appear to "pop out" */
ul#tabMenu li.active, ul#tabMenu li a:hover {
    padding: 0.5em 0.5em 0.2em 0.5em;
}

/* tab content */
.tabContent {
    background-color: #f7f7f7;
    padding: 20px;
    border: 1px solid #aaa;
    border-top-style: none;
}
-- cut --