Remove obsolete Masonry CSS styles.
Add JSHint and adjust its configuration for masonite.js; whitespace, doublequotes.
Only define "sans-serif" as default font (remove "Arial"); previously this caused problems with Tumblr's "Customize"-control, now it seems to work fine.

The only problem now is that once you pick a custom font, you can't switch back to the theme default … but that's another story.
We're certainly not getting worse by throwing out Arial.
Newlines.