CSS fixes

Hi sajolida!

This is a ticket about my merge request issued on tails-dev. I’ve made the requested improvements by you and intrigeri (except for the logo (yet)) and would like you to review and merge this asap. Thanks!

Feature Branch: 451f:tails/feature/smallCSSfixes

Parent Task: #12035 (closed)

Original created by @u on 14821 (Redmine)

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