function toggle_video(which)
{
    for ( var d = 0; d <= 7; ++d )
    {
        document.getElementById("video"+d).style.display 
           = ( d == which ) ? "block" : "none";
    }
}

function toggle_text(which)
{
    for ( var d = 0; d <= 7; ++d )
    {
        document.getElementById("text"+d).style.display 
           = ( d == which ) ? "block" : "none";
    }
}