.back-to {
    display: none;
    background: transparent url(back.png) no-repeat center center;
    width: 44px;
    height: 44px;
    color: transparent;
    /* Hide text */
    text-indent: 100%;
    white-space: nowrap;
    overflow: hidden;
    /* Correct positioning */
    position: absolute;
    z-index: 1000;
    right: -44px;
}

/**
 * Security: when you do a subception or a supception each item will
 * inherit of a font-size such as 80% or 90% of its parent. Doing a
 * *ception here would cause the size to drop down until it reaches
 * less than 6px; Once you reach this size most browsers will drop the
 * size to 0px which will hide the text and allow the user to put non
 * visible content, such as either one of viagra advertisement or
 * malicious code in a code block area (copy/paste attack). This one
 * liner will avoid text to be hidden and fix this.
 */
sup sup sup sup, sub sub sub { font-size:100% }