Ad below post 1.7

// advertising responsive

.advertising-wide
{
    display: inline;
    text-align: center;
}

.advertising-narrow
{
    display: none;
}

@media (max-width: @xf-responsiveMedium)
{
    .advertising-wide
    {
        display: none;
    }
 
    .advertising-narrow
    {
        display: inline;
        text-align: center;
    }
}