.nav-tabs > li, .nav-pills > li {
    float:none;
    display:inline-block;
    *display:inline; /* ie7 fix */
     zoom:1; /* hasLayout ie7 trigger */
}

.nav-tabs, .nav-pills {
    text-align:center;
}

by http://stackoverflow.com/questions/9421966/how-do-i-center-the-twitter-bootstrap-tabs-on-the-page