How to add CSS parameter to the shortcode?

Hi,

could you please give an example how to add the CSS parameter to the shortcode?

In my case, this does not work:

normal shortcode:
[widget id="avia_auto_toc-4"]

Now I need the container in some cases with floating right, so I add to the shortcode:

[widget id="avia_auto_toc-4" container_class="floatright"]

and the corresponding CSS is:

#top #avia_auto_toc-4.floatright {
    float: right;
    margin-left: 30px;
    width: 50%;
    margin-top: 0px;
    background-color: #f0edee;
    padding: 0px;
    margin-bottom: 30px;
}

But it does not float right; so perhaps I have not correctly added the class to the shortcode?

Thanks.