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

/* standard Firefox 2 and Minefield */
.tabbrowser-tab:focus .tab-text,
/* Tab Mix Plus */
.tabbrowser-tabs[firefox2notMac] > .tabbrowser-tab:focus .tab-middle .tab-text {
   border: 1px dotted transparent !important;
}