CSS boostrap

boostrap.css

.carousel .active {
    left: 0;
}
bootstrap.css (línea 3267)
.carousel .active, .carousel .next, .carousel .prev {
    display: block;
}
bootstrap.css (línea 3264)
.carousel .item {
    -moz-transition: left 0.6s ease-in-out 0s;
    display: none;
    position: relative;
}

index.html

                  <div class="item active">
                    <img src="bootstrap/img/visio1.jpg" alt="" class="center">
                    <div class="carousel-caption">
                      <h4>First Thumbnail label</h4>
                      <p>Cras justo odio, dapibus ac facilisis in, egestas eget quam. Donec id elit non mi porta gravida at eget metus. Nullam id dolor id nibh ultricies vehicula ut id elit.</p>
                    </div>
                  </div>

vindes.css

.carousel .item > img.center  {
    display: block;   margin-left: auto;   margin-right: auto;
}