@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);

.tabbrowser-tab[selected="true"]
{
    -moz-appearance: -moz-win-glass !important;
    background: none !important;
    background-color: grey !important;
    opacity: 0.99 !important;
    -moz-border-top-colors: rgba(0,0,0,0.6) grey !important;
    -moz-border-left-colors: rgba(0,0,0,0.6) grey !important;
    -moz-border-right-colors: rgba(0,0,0,0.6) grey !important;
}

.tabs-bottom 
{
 -moz-appearance: -moz-win-glass !important;
    background: none !important;
    background-color: grey !important;
    opacity: 0.99 !important;
}