Focus issue causes screen to jump

[Ipstenu]

When you view a theme (i.e. ​https://wordpress.org/themesnew/make/ ) and your screen is smaller than the screenshot, your page jumps after load.

First you see this:

Then it JUMPS to this:

Clearly it's the focus on the download button that's doing this :/

[obenland]

In 1255:

WP.org Themes: First pass at revised modal styles.

Props melchoyce.

See ​http://make.wordpress.org/meta/2015/01/23/theme-directory-mockups/
Fixes missing forum link for #852,
Fixes #847.