Two Line Site Title / with varying sizes

Site URL: http://www.regencampos.es

I would like to add a smaller subtitle to the Site Title in the header.

So:

SiteTitle

subtitle

I have used a code injection from SF Digital (pasted elsewhere) to replace '|' symbols in the SiteTitle text with <br>, but it's not working. I'd also like to change the font size. 

If I could use a code block for a site title this would be very easy indeed. 

Anybody?

What is access password?

For anyone interested, this is the code that worked: 

/* sub title */

a#site-title:after {

    content: "Subtitle Text";

    display: block;

    font-size: 15px;

}

Thanks Tuan!