Different Style for Mobile?

[DarrenS]

I see that vB5 has removed the settings for choosing a different style to serve to mobile browsers. I understand that the intention is for styles to be responsive.

However I want to make different style choices in serving the forum to desktop and to mobile users (mostly in the header). In Googling I've seen references to using specific CSS classes to modify mobile in distinct ways within css_additional. So, two questions:

(1) Is there a guide or documentation that explains how to do this?

(2) Are modifications limited to CSS, or are there also conditional tags I can apply to the header template (e.g., so that a block of HTML code only appears on desktop)?

Thanks!