Remove website/blog title

Hi

I want to add a small logo inside the site logo div inside the branding div in the default theme for the Firectory plugin.

I can get the logo in there using css - e.g. #site-logo {background-image: url("...etc...");} but I still get the site title sitting there as well.

How can I hide the site title so I see only the inserted logo? And what would the optimal size (height/width) for a logo inserted into the site-logo div be?

Many thanks

Rick