The PanelPositioned component renders a visible xml comment containing a random number. The rendered comment only appears visible on some browsers, such as Chrome and IE, but not others, such as Firefox. The xml comment is being rendered in the following section of PanelPositionedRenderer:

             if (isChanged(facesContext)) {
                    // Force the re rendering of the entire component. This is due to a strange quick with positioned
                    // panel. When an element is moved in the same list then it container element moves with it
                    // When the update occurs the elements are replaced but because the containers have moved
                    // then the result looks the same. (But a refresh shows otherwise)
                    Node node = domContext.createTextNode(
                            "<!-- " + (new Random().nextInt(1000)) + "-->");
                    root.appendChild(node);
                }