The reasons for this change are:
- better compression
- clean-css works around a couple of old IE issues like the one which needs a space after comma in
filter
properties (hence bootstrap-theme.min is bigger with clean-css) - clean-css is in active development and next thing is to improve selectors merging so compression should improve even more
For bootstrap.min.css
102.931 master.css
100.728 clean-css.css
/CC @mdo