[fixup/valid_css] Fix invalid CSS and/or HTML

B3P-118
[fixup/theme] Fix theme paths and topic icons

B3P-118
Merge pull request #129 from marc1706/fixup/valid_css

[fixup/valid_css] Fix invalid CSS and/or HTML
Merge pull request #130 from marc1706/fixup/theme

[fixup/theme] Fix theme paths and topic icons